Documents published in 2020 : Scipedia

TIEMPOS DE PANDEMIA
R. Gasperi Romero

Revista Venezolana de Salud Publica (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
Estamos viviendo tiempo de pandemia de un virus tipo coronavirus el COVID 19, causante de una enfermedad que si bien el 80% de la población cursa como una gripe cualquiera con catarro, dolor de garganta, malestar general, tos, fiebre y se mejora rápidamente, en un 20% de la población este puede causar más daño prolongándose y profundizándose sus síntomas causando daños respiratorios, cardiovasculares y deterioro del estado general ameritando la hospitalización, tratamiento médico específico, algunos necesitaran apoyo ventilatorio en una UCI y un 2% de estos pacientes morirán . Es por ello que debemos estar conscientes de la situación que enfrentamos; una pandemia, un caso inédito en la historia reciente de la humanidad con repercusiones globales no solo desde el punto de vista Sanitario sino social y económico.
Abstract
Estamos viviendo tiempo de pandemia de un virus tipo coronavirus el COVID 19, causante de una enfermedad que si bien el 80% de la población cursa como una gripe cualquiera [...]
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DR. OSWALDO VALDIVIA: DOCENTE E INVESTIGADOR ÍCONO DE LA UNIVERSIDAD CENTROCCIDENTAL LISANDRO ALVARADO.
A. Elías, D. Eduardo, D. Esthefany

Revista Venezolana de Salud Publica (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
El Doctor Oswaldo Valdivia nació en 1937 en Arequipa, Perú. En 1958 inició sus estudios en la carrera de medicina, en el primer año nació el amor por la neuroanatomía y en el cuarto año inicio su labor como docente. Se graduó como médico en 1964 y de anatomopatólogo en 1966. Contrajo matrimonio en 1962 con Zulema Valdivia con quien tuvo 3 hijos, en 1968 fue becado para entrenamiento de microscopia electrónica en la universidad de Wisconsin. En 1973 decidió emigrar hacia Venezuela debido a la situación del Perú y por una oferta laboral de parte de la Universidad Centroccidental Lisandro Alvarado (UCLA), donde se desenvolvió como profesor de anatomía microscópica a dedicación exclusiva, ampliadas contribuciones como la incorporación de la microscopia electrónica en la región centroccidental del país en 1980. Realizó diversos trabajos de investigación, principalmente sobre leishmaniasis, fue profesor jubilado activo de la UCLA hasta sus últimos días. En su ejercicio profesional dio grandes aportes a la salud pública, participando en jornadas de pesquisa de patológica cervical y formando profesionales de la salud. Fallece el 18 de noviembre de 2019 en Perú, su tierra natal.
Abstract
El Doctor Oswaldo Valdivia nació en 1937 en Arequipa, Perú. En 1958 inició sus estudios en la carrera de medicina, en el primer año nació [...]
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THE AGRIFOOD AND PUBLIC HEALTH IN VENEZUALA. A VISION FROM COMPLEX THOUGHT
M. Yesenia, C. Salvador, J. Erika

Revista Venezolana de Salud Publica (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
This essay is based on the development of a body of argumentation of reality in agrifood and public health that underpins the agrifood model of hegemonic domination, thus justifying the importance of the transformation of productive economic development, its relations with the Public health, from the complexity of reality, living conditions and social reproduction, that is why the advancement of a grounded theory that guides agri-food development in the sphere of production, distribution, consumption, access to feeding opportunities in Venezuela and their relationship with the world in the context of environmental preservation and life from the paradigm of complexity, using the hermeneutical method with the use of dialectics as a strategy in discursive argumentation
Abstract
This essay is based on the development of a body of argumentation of reality in agrifood and public health that underpins the agrifood model of hegemonic domination, thus [...]
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LIFESTYLE MEDICINE. AN ALTERNATIVE TO THE ADVANCE OF NON TRANSMISSIBLE DISEASES
B. Giovanna, M. Ahimara

Revista Venezolana de Salud Publica (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
Lifestyle Medicine (MdelEV) has gained relevance in the prevention, treatment and reversal of most chronic diseases, directly addressing its underlying causes. Based on the foregoing, this article aimed to carry out a descriptive review of fundamental elements that characterize Lifestyle Medicine, its advances in clinical research in the areas of nutrition, exercise and stress reduction, as well as the growing trend of make it an integral component of the curricula of medical schools. An exhaustive search was carried out in different documentary sources, using the categories Lifestyle Medicine, basic principles of Lifestyle Medicine, Conventional Medicine vs.. Lifestyle Medicine, clinical studies at MdelEV, as well as lifestyle medicine as a medical subspecialty. Approximately 60 abstract scientific articles were reviewed. Through the use of inclusion criteria, 27 articles were selected and subjected to a comprehensive and analytical reading. In the development and discussion of the subject, the results of the review are presented, highlighting the use of the model of social determinants of health proposed by the WHO, findings of experimental research on the reversal of risk factors in STDs, and advances in training professional. In the discussion they combine the results of all the selected articles with a critical position.
Abstract
Lifestyle Medicine (MdelEV) has gained relevance in the prevention, treatment and reversal of most chronic diseases, directly addressing its underlying causes. Based [...]
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ZOONOSIS AS A PUBLIC HEALTH PROBLEM FROM A COMPREHENSIVE VISION
S. Carolina, T. Zulay

Revista Venezolana de Salud Publica (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
Zoonoses as the result of a process where various factors intervene and are related to epidemiological, economic and social variables, this article reviewing the was developed, with the aim of reflecting on the contextualization of the control programs of the Zoonosis as a public health problem, for the reflexive argumentation of this document, a documentary review was carried out, with extraction, compilation of information, and analysis of the theoretical foundations and the results presented in the consulted investigations, visualizing the criteria described by different authors, which can be of great contribution due to the little information on communicable diseases from animals to humans and the actions of INSAI, as the governing body for addressing zoosanitary and phytosanitary problems, highlighting as a conclusion the need for training of the staff, participated n active, interdisciplinary of human and animal health professionals.
Abstract
Zoonoses as the result of a process where various factors intervene and are related to epidemiological, economic and social variables, this article reviewing the was developed, [...]
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SATISFACTION IN THE PROVISION OF HEALTH SERVICES IN OLDER ADULTS COLOMBIA 2018
M. Villa, J. -Jiménez, M. Villamil-Gallego,, Á. Quintero-Echeverri, C. Robledo

SATISFACCIÓN EN LA PRESTACIÓN DE SERVICIOS DE SALUD EN ADULTOS MAYORES COLOMBIA 2018 (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
The term active aging is relatively new and very little known, although much has been said about this in recent times. The objective of this work to review the literature on health care for the elderly. The method used a narrative review through an exploration of exploration of scientific articles in the databases: Science direct, Pubmed and Scielo. In the results it was found that in several articles the elderly were not satisfied with the care they received in health. In conclusion, as reported by older people, there is a large gap between what is said in public policies on aging and what is actually being done in the provision of services. Regarding the perception that older adults have of their health in Antioquia, there is a very high percentage that believes that health care is not adequate
Abstract
The term active aging is relatively new and very little known, although much has been said about this in recent times. The objective of this work to review the literature [...]
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ENTERIC PARASITOSIS IN SCHOOL CHILDREN: IMPORTANCE OF ASSOCIATED PARASITES
R. Devera,, A. Soares, D. Rayarán, I. Amaya, Y. Blanco

Revista Venezolana de Salud Publica (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
Simultaneous presence of various enteric parasites can have important clinical, epidemiological and therapeutic implications. A retrospective study of correlational type was carried out to determine Fager’s Affinity Index in a group of polyparasitized schoolchildren from Bolivar state, Venezuela. Between 2007 and 2016, 1277 children between 5 and 15 years of age from 11 schools (10 in the Heres municipality and 1 in the Caroní municipality) were evaluated. Gender distribution was homogeneous in the schoolchildren evaluated (n = 613 female and n = 664 male). Of the 1277 samples analyzed, 811 (63.7%) showed enteric parasites in their evolutionary form. The most common were the chromists represented by Blastocystis spp. (49.3%), followed by the protozoa Endolimax nana (14.5%) and Entamoeba coli (11.7%), and lastly the helminths, where the most frequent was Ascaris lumbricoides (5.5%). Schoolchildren were polyparasitized in 43.2% of cases, the most commonly associated parasite being Blastocystis spp. with 90% of cases followed by E. nana (43.1%) and E. coli (35.4%). The affinity indices (IAB) and "t" tests carried out indicated an association between Blastocystis spp. and the protozoa G. intestinalis, E. nana and E. coli and between Trichuris trichiura and A. lumbricoides geohelminths.
Abstract
Simultaneous presence of various enteric parasites can have important clinical, epidemiological and therapeutic implications. A retrospective study of correlational type was [...]
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ARTERIAL HYPERTENSION AND SOCIAL LONELINESS IN AN OLDER POPULATION FROM 55 YEARS AND OLDER. BARQUISIMETO, VENEZUELA
R. Vicencina, A. Jesús, B. Celis, C. Carlos, D. Nelson, D. Esthefany, E. al

Revista Venezolana de Salud Publica (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
Social loneliness has been shown to be closely related to the health status of the population. The present research assessed the prevalence of arterial hypertension and its association with the perception of social loneliness in residents over 55 years of age in the Antonio Carrillo community. In this regard, an analytical prevalence study, 92 people were studied as population, the previous diagnosis of arterial hypertension was asked, blood pressure was measured, and the data collection tool ESTE II was subsequently applied. It was found that, in the population over 55 years of age, according to the general characteristics of the population, the female sex predominated (63%); in addition, the majority of the habitants were between the ages of 55 and 64 (52.2%); according to marital status, married residents prevailed (41.3%); with regard to education, the majority of the population underwent incomplete primary education (24%) and in regards of the inactivity by the unemployment situation (76.1%). 65.2 % of the population was found to be hypertensive, and in terms of the perception of social loneliness, 68.5% of the population was found to have the same conditions. As in fact, when the association between blood pressure and the perception of social loneliness was made, it was specified that 68.3% of the habitants with perception of social loneliness were hypertensive (p>0.05).
Abstract
Social loneliness has been shown to be closely related to the health status of the population. The present research assessed the prevalence of arterial hypertension and its [...]
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Prueba tbala
. ðﾝﾑﾽ, H. Tabares-Ospina

(Select a year).
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PREDICT CLINICAL METABOLIC ABNORMALITIES BY WAIST TO HEIGHT RATIO DEPENDS ON THE MEASURING SITE.
M. Adaucio, M. Mariela.

PREDECIR ALTERACIONES CLÍNICO–METABÓLICAS MEDIANTE EL ÍNDICE CIRCUNFERENCIA ABDOMINAL-TALLA DEPENDE DEL SITIO DE MEDICIÓN. (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
Aim: To determine the ability of the waist to height ratio to predict two or more clinical – metabolic disorders, according to site measuring of waist circumference. Methods: A crosssectional analytical observational study was made. 800 adolescents, between 15 and 19 years old, of both sexes (405 men), enrolled in 31 institutions of secondary and university education of Iribarren Municipality Lara – Venezuela were studied. Adolescents signed an informed consent. Socioeconomic status, dietary habits, physical activity, height and waist circumference at three anatomical sites: above the iliac crests, midpoint of abdomen and below costal margin were assessed. Waist to height ratio for each site was calculated. Next, blood pressure, serum glucose and serum lipids were evaluated. Bivariate statistical analysis and logistic regression were performed. Results: It was possible to model the presence of two or more clinical – metabolic disorders as a function of the waist to height ratio, both below the costal margin and above the iliac crests. However, the degree of association varied according to anatomical site, with a higher probability of two or more clinical disorders metabolic in the first site. Such probability was directly proportional to the waist to height ratio and higher in men. Conclusion: Upper abdominal fat predicted better two or more clinical – metabolic disorders compared to the lower abdominal fat. Given these results, it could unify the anatomic site to measure of waist circumference, just below the costal margin, to identify adolescents with higher probability for such disorders, as risk factors for cardiovascular disease.
Abstract
Aim: To determine the ability of the waist to height ratio to predict two or more clinical – metabolic disorders, according to site measuring of waist circumference. [...]
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WORK ACCIDENTS AND DISABILITY IN MUNICIPAL POLICE OF IRIBARREN OF DE LARA STATE
A. Noryesca, M. Najul

ACCIDENTES DE TRABAJO Y DISCAPACIDAD EN POLICÍAS MUNICIPALES DE IRIBARREN DEL ESTADO LARA (2020). http://revistas.ucla.edu.ve/index.php/rvsp

Abstract
The objective of this research was to determine the characteristics of work accidents and disability in the municipal police of Iribarren, Lara state. The study was framed in a descriptive, transversal field research. A target population of 297 workers of said security body was selected. A previously validated questionnaire was applied through the trial of three experts, using the interview technique, in order to determine the sociodemographic and work aspects of the police, the epidemiological and occupational characteristics of work accidents, clinical and work characteristics of work accidents and disability according to clinical-legal aspects. The most significant results were: 37.71% of the policemen were aged 33-37 years, 88.55% were male, their educational level was secondary at 50.84%, marital status is 54.88%, 84.85% had a mixed shift, the operational range was 94.61%, 41.08% of the police officers were officers added, in terms of seniority it is 6 to 10 years in 51.85%. The frequency of accident was 59.60%, of the instruments that caused the accidents were firearms, 57.85%, the activity carried out at the time of the accident was patrolling at 22.60%, the type of accident was for the fact at 51, 98%, 73.45% of the police officers did not notify the accident, the anatomical site most affected were the upper limbs 27.68%, the severity of the injury was severe in 42.37%, the most common type of disability was the partial permanent at 38.42%. This study is a contribution for the Municipal Police and for similar organizations, because their results provide statistical data that could be used to carry out preventive programs that allow finding solutions to the problem of work accidents and disability.
Abstract
The objective of this research was to determine the characteristics of work accidents and disability in the municipal police of Iribarren, Lara state. The study was framed [...]
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Los trabajos de fans como crítica
B. García de Pablos

(2011). Universitat Oberta de Catalunya, 2011

Abstract
Habitualmente se piensa que los fans y los trabajos hechos por fans se basan únicamente en la adoración de éstos por los textos de origen, pero esto no es cierto: los fans son muchas veces los críticos más feroces ya que, al conocerlos tan bien y formar parte de una comunidad en torno al texto, son capaces de encontrar recursos (literarios, cinematográficos, etc.) recurrentes que muchas veces contienen elementos machistas, racistas o similares, que los fans pasan a criticar; en otros casos es el mismo texto el que les permite hacer una crítica de la sociedad; y en otros, los fans se sienten traicionados por el autor del texto base y pasan a criticar la actitud de éste. Estas críticas pueden realizarse de muy distintas maneras: ya sea por medio de textos escritos en las que se analiza el texto base, por medio de relatos, películas, cómics, vídeos u otros en los que se expone la crítica. Son en los trabajos creativos (relatos/películas/vídeos) realizados por fans en los que nos centraremos, ya que son los que se alejan más de la crítica tradicional y, aunque formalmente algunos de ellos puedan estar más cerca de la parodia o la sátira, el fondo normalmente se aleja de ellas tanto por la relación de los fans con el texto, como por el contenido de las mismas.
Abstract
Habitualmente se piensa que los fans y los trabajos hechos por fans se basan únicamente en la adoración de éstos por los textos de origen, pero esto no [...]
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Proper Use of Technical Standards in Offshore Petroleum Industry
D. Brkić, P. Praks

Journal of Marine Science and Engineering (2020). 8(8), article 555

Abstract
Ships for drilling need to operate in the territorial waters of many different countries which can have different technical standards and procedures. For example, the European Union and European Economic Area EU/EEA product safety directives exclude from their scope drilling ships and related equipment onboard. On the other hand, the EU/EEA offshore safety directive requires the application of all the best technical standards that are used worldwide in the oil and gas industry. Consequently, it is not easy to select the most appropriate technical standards that increase the overall level of safety and environmental protection whilst avoiding the costs of additional certifications. We will show how some technical standards and procedures, which are recognized worldwide by the petroleum industry, can be accepted by various standardization bodies, and how they can fulfil the essential health and safety requirements of certain directives. Emphasis will be placed on the prevention of fire and explosion, on the safe use of equipment under pressure, and on the protection of personnel who work with machinery. Additionally considered is how the proper use of adequate procedures available at the time would have prevented three large scale offshore petroleum accidents: the Macondo Deepwater Horizon in the Gulf of Mexico in 2010; the Montara in the Timor Sea in 2009; the Piper Alpha in the North Sea in 1988.
Abstract
Ships for drilling need to operate in the territorial waters of many different countries which can have different technical standards and procedures. For example, the European [...]
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PLAN DE NEGOCIOS
A. Quintero

Annia Quintero's personal collection (2020). 1

Abstract
Occicorps Cosmetics, C.A. es una empresa conformada por la Corporación Occipital (constituido por Adriana Castellanos, Annia Quintero, Thalía Samarjian, Miguel Tovar y Glen Zea), y surge como una iniciativa privada de cinco jóvenes farmacéuticos que desean atender las necesidades de negocio de empresas pequeñas a medianas que requieran fabricar productos cosméticos y de cuidado personal, pero que no cuentan con el conocimiento, instrumentos, o las instalaciones para concretar sus proyectos. Occicorps Cosmetics C.A. presenta un plan de negocios como una empresa dedicada al diseño, producción y almacenamiento de productos cosméticos líquidos y semisólidos de pequeña a mediana escala, contribuyendo al desarrollo de otros emprendedores. Diseñamos y producimos cosméticos de alta calidad. Este plan de negocios tiene como propósito dar a conocer el objetivo general y los objetivos específicos de la empresa, aunado a nuestra razón de ser como la misión, visión y los valores que rigen a la compañía. También exponemos el abanico de servicios que estamos en la posibilidad de ofertar y estrategia de marketing. A partir de esta información, se evaluará la rentabilidad y viabilidad de la empresa.
Abstract
Occicorps Cosmetics, C.A. es una empresa conformada por la Corporación Occipital (constituido por Adriana Castellanos, Annia Quintero, Thalía [...]
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Project B2 - Evaluation of Work Zone Mobility by Utilizing Naturalistic Driving Study Data
H. Zhou, R. Turochy, D. Xu

Collection of Research Data in Transport (2020). 2

Abstract
The purpose of this research is to evaluate work zone mobility using SHRP2 NDS naturalistic driving data. In this study, forward, rear-view video, and time series traces for traversed work zones are collected at 0.1 second intervals. Using the forward and rear-ward videos work zone configurations such as traffic control devices, area types, presence of dynamic message signs (DMS), intelligent transportation systems technologies (ITS), as well as the presence of workers and equipment are identified. These videos are also used for estimating traffic density by observing the number of vehicles surrounding the participant, and average traffic flow by observed speed and traffic density. The capacities of different work zone sections and configurations are estimated based on developed speed-flow relationships and this capacity is used to verify and calibrate the work zone capacity method defined by the newest addition of Highway Capacity Manual (HCM). The probability of breakdown is then estimated for each level of flow rates and volume to capacity ratios can be used to verify the results of HCM.
Abstract
The purpose of this research is to evaluate work zone mobility using SHRP2 NDS naturalistic driving data. In this study, forward, rear-view video, and time series traces [...]
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CLOUD TECHNOLOGY: A CATALYST FOR EFFECTIVE ENTREPRENEURSHIP EDUCATION IN NIGERIA
. AKPANOBONG, U. AKPANOBONG

Nigerian Journal of Business Education (2017). Alghali, M., Alwi, N. H. M., & Ismail, R. (2013). Privacy in cloud based e-Learning. The Second International Conference on Informatics Engineering & Information Science (ICIEIS2013). pp. 355-362. The Society of Digital Informationand Wireless Communication. Alghali, M., Alwi, N. H. M., and Ismail, R. (2014). Challenges and benefits of implementing cloud-based e-learning in developing countries. Proceeding of the Social Sciences Research (ICSSR-2014). pp. 9-10. Amue, G. J., Igwe, S. R. & Abiye, H. (2014). ICT entrepreneurship and small business innovation: A mechanism for sustainability. European Journal of Business and Social Sciences, 3 (6), pp. 103 -112. Retrieved May 20, 2016 from http:// www.ejbss.com/recent.aspx Armbrust, M., Fox, A., Griffith, R., Joseph, A. D., Katz, R. H., Konwinski, A. Zaharia, M. (2009, February 10). Above the clouds: A Berkeley view of cloud computing. Retrieved from http://www.eecs.berkeley.edu/Pubs/TechRpts /2009/EECS-2009- 28.html Eken, H. (2014). Cloud computing security issues and recommendations. International Journal of Intelligent Computing Research (IJICR), 5 (1/2). Ercan, T. (2010). Effective use of cloud computing in educational institutions. Procedia Social and Behavioral Sciences 2, pp. 938-942. Tadapaneni, N. R. (2017). Different Types of Cloud Service Models. Available at SSRN 3614630. Gkikas, D. (2014). The impact of cloud computing on entrepreneurship and Start-ups: case of Greece. Sweden: KTH Industrial Engineering and Management. Larry, C. K. & Best, Z. Y. (2011). The use of ICT in entrepreneurial development. Journal of Research in Entrepreneurship, 16 (6), 339-352. Hamburg, I. & Brien, E. O. (2014). Cloud computing to support e-learning and business in SMEs. International Journal for e-learning Security (IJeLS),4 (3,4). Hamburg, I., Bucksch, S. & Brien, E. O. (2015). ICT–based approaches for Entrepreneurship education. The Tenth International Conference on Internet and Web Application and Services ICIW. Marston, S., Li, Z., Bandyopadhyay, S., Zhang, J. & Ghalsasi, A. (2011). “Cloud computing – The business perspective”. Decision Support Systems, 51, pp. 176- 189. Mathew, S. (2012). Implementation of cloud computing in education – A revolution. International Journal of Computer Theory and Engineering, 4 (3). Mell, P. & Grance, T. (2011). The NIST definition of cloud computing, Recommendation of the National Institute of Standards and Technology (draft). NIST Special Publication, 800 (145), 7. Odunaike, S. A., Olugbara, O. O., & Ojo, S. O. (2012). Using cloud computing to mitigate rural e-learning sustainability and challenges. Proceedings of the World Congress on Engineering and Computer Science, 1. San Francisco, USA. Seleman, Y. E. A. (2015). Modern methods in the development of education using cloud computing applications. Global Journal of Computer Science and Technology: B Cloud and Distributed, 15 (2, 1) Staten, J., Schadler, T., Rymer, J. R. & Wang, C. (2009). Q & A : By 2011, CIOs must answer the question, “Why not run in the cloud ?” (Leaver, S. and Viglianti, A. Interviewers). Sclater, N. (2010). Cloud computing in education. Institute for Information Technologies in Education (IITE). Policy Brief. UNESCO. Retrieved August, 26, 2016 from http://iite.unesco.org/pics/publications/en/files/3214674.pdf Yadav, K. (2014). Role of cloud computing in education. International Journal of Innovative Research in Computer and Communication Engineering, 2 (2).

Abstract
Information technology plays a major role in organising and operating a business by any entrepreneur. Entrepreneurship involves the ability to be creative, innovative and taking risk as well as the capability to plan and manage projects to achieve the set objectives. Entrepreneurship education contributes to economic growth in developed nations. The financial crisis and the economic recession being experienced now in the country has really affected the entrepreneurs who operate Small and Medium Scale Enterprises (SMEs) in Nigeria due to inability to explore modern technology in their businesses. Therefore, there is need for cloud technology to be adopted as a powerful catalyst that would enhance job creation through entrepreneurship education. The potential for cloud computing to boost entrepreneurs as a platform for entrepreneurship education is significant. This technology can be adapted to support entrepreneurship education as it can be scaled over time to offer the required resources. Research has shown that cloud computing has played a catalytic role in boosting education in the world. Thus, the paper examined the potential benefits and issues involved in adopting cloud computing to support entrepreneurship education. It was concluded that the adoption of cloud computing would help to generate thousands of new jobs in Nigeria. It was also recommended among others that the National Information Technology Development Agency should organise workshops, seminars and training for existing entrepreneurs on the benefits of using cloud technology. Cloud technology should also be introduced as one of the courses in business education and allied fields.
Abstract
Information technology plays a major role in organising and operating a business by any entrepreneur. Entrepreneurship involves the ability to be creative, innovative and [...]
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The solution of non‐linear hyperbolic equation systems by the finite element method
R. Lohner, K. Morgan, O. Zienkiewicz

International Journal for Numerical Methods in Fluids (1984). Vol. 4 (11), pp. 116-120

Abstract
The difficulties experienced in the treatment of hyperbolic systems of equations by the finite element method (or other) spatial discretization procedures are well known. In this paper a temporal discretization precedes the spatial one which in principle is considered along the characteristics to achieve a self adjoint form. By a suitable expansion, the original co‐ordinates are preserved and combined with the use of a standard Galerkin process to achieve an accurate discretization. It is shown that the process is equivalent to the Taylor‐Galerkin methods of Donea.17 Several examples illustrate the accuracy and efficiency attainable in such problems as transport, shallow water equations, transonic flow etc.
Abstract
The difficulties experienced in the treatment of hyperbolic systems of equations by the finite element method (or other) spatial discretization procedures are well known. [...]
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Accelerated ‘relaxation’ or direct solution? Future prospects for fem
R. Lohner, O. Zienkiewicz

International Journal for Numerical Methods in Engineering (1985). Vol. 21 (1), pp. 1-11

Abstract
‘Dynamic’ or ‘viscous’ relaxation procedures have not gained much popularity in finite element analysis in which the direct (Gaussian elimination) solution dominates. Reasons for this are various—the most important being the rather slow convergence generally achieved for such procedures. However, it is possible to accelerate this quite dramatically and a method of doing so is shown in this paper. With the use of such acceleration and the inherent advantages of greatly reduced storage requirements and simplicity of programming, relaxation procedures promise an exciting possibility for the solution of large two‐ and three‐dimensional problems in both linear and nonlinear ranges.
Abstract
‘Dynamic’ or ‘viscous’ relaxation procedures have not gained much popularity in finite element analysis in which the direct (Gaussian elimination) [...]
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Recent developments in FEM-CFD
R. Lohner, K. Morgan, J. Peraire, O. Zienkiewicz

(1985). The Free-Lagrange Method. Lecture Notes in Physics, vol 238. Springer, Berlin, Heidelberg

Abstract
The current status of CFD with regard to unstructured grids employing finite element methods and Eulerian frames is reviewed. Algorithms suitable for the computation of large three-dimensional problems involving flow past arbitrary geometries are developed. Adaptive mesh refinement strategy is reviewed, and domain splitting or local time-stepping are briefly addressed. The development of search algorithms of optimal order, variable time-stepping Jacobi smoothers for elliptic problems, and transport concepts for hyperbolics to help achieve good performance for unstructured multigrid processes is discussed. As examples, transient supersonic flow in a channel, regular shock reflection of a wall, viscous flow past a protruberance, potential flow past a cylinder, and Burgers equation are considered.
Abstract
The current status of CFD with regard to unstructured grids employing finite element methods and Eulerian frames is reviewed. Algorithms suitable for the computation of large [...]
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A simple extension to multidimensional problems of the artificial viscosity due to Lapidus
R. Lohner, K. Morgan, J. Peraire

Communications in numerical methods in engineering (1985). Vol. 1 (4), pp. 141-147

Abstract
An artificial viscosity suitable for use in the simulation of multidimensional high-speed compressible flows by the finite element method is proposed. The form adopted is a consistent extension of the method due to Lapidus.
Abstract
An artificial viscosity suitable for use in the simulation of multidimensional high-speed compressible flows by the finite element method is proposed. The form adopted is [...]
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An adaptive finite element procedure for compressible high speed flows
R. Lohner, K. Morgan, O. Zienkiewicz

Computer Methods in Applied Mechanics and Engineering (1985). Vol. 51 (1-3), pp. 441-465

Abstract
A two-step explicit finite element procedure for obtaining time-accurate solutions to the compressible Euler equations is described. The method is coupled with an adaptive mesh refinement process which enables steady state solutions of improved quality to be obtained.
Abstract
A two-step explicit finite element procedure for obtaining time-accurate solutions to the compressible Euler equations is described. The method is coupled with an adaptive [...]
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Effective Programming of Finte Element Methods for Computational Fluid Dynamics on Supercomputers
R. Lohner, K. Morgan, O. Zienkiewicz

(1986). The Efficient Use of Vector Computers with Emphasis on Computational Fluid Dynamics. Notes on Numerical Fluid Mechanics, vol 12. Vieweg+Teubner Verlag, Wiesbaden

Abstract
The effective programming of Finite Element Methods for CFD on vector-machines is discussed. It is shown, that for unstructured grids the performance observed on this class of machine depends heavily of the availability of hardware Gather/Scatter. Timings obtained for a 3-D Euler code are presented for the CYBER-205, CRAY-XMP11 and CRAY-XMP48.
Abstract
The effective programming of Finite Element Methods for CFD on vector-machines is discussed. It is shown, that for unstructured grids the performance observed on this class [...]
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Unstructured multigrid methods for elliptic problems
R. Lohner, K. Morgan

International Journal for Numerical Methods in Engineering (1987). Vol. 24 (1), pp. 3323-3331

Abstract
A multigrid algorithm for implementation on unstructured meshes is proposed. The algorithm uses a sequence of unnested grids and requires the development of efficient inter-grid interpolation procedures. It is demonstrated how elliptic problems can be solved in this fashion by using Jacobi smoothers
Abstract
A multigrid algorithm for implementation on unstructured meshes is proposed. The algorithm uses a sequence of unnested grids and requires the development of efficient inter-grid [...]
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An adaptive finite element scheme for transient problems in CFD
R. Lohner

Computer Methods in Applied Mechanics and Engineering (1987). Vol. 61 (6), pp. 323-338

Abstract
An adaptive finite element scheme for transient problems is presented. The classic h-enrichment / coarsening is employed in conjunction with a triangular finite element discretization in two dimensions. A mesh change is performed every n timesteps, depending on the Courant number employed and the number of ‘protective layers’ added ahead of the refined region. In order to simplify the refinement/ coarsening logic and to be as fast as possible, only one level of refinement/coarsening is allowed per mesh change. A high degree of vectorizability has been achieved on the CRAY XMP 12 at NRL. Several examples involving shock-shock interactions and the impact of shocks on structures demonstrate the performance of the method, indicating that considerable savings in CPU time and storage can be realized even for strongly unsteady flows.
Abstract
An adaptive finite element scheme for transient problems is presented. The classic h-enrichment / coarsening is employed in conjunction with a triangular finite element [...]
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Finite elements in CFD: What lies ahead
R. Lohner

International Journal for Numerical Methods in Engineering (1987). Vol. 24 (9), pp. 1741-1756

Abstract
The current state of the art of Finite Element Methods in Computational Fluid Dynamics is reviewed. The aim of this review is to point out what appear currently as the main shortcomings of Finite Element Methods, so as to concentrate the efforts to remove them. The analysis of flows using Finite Elements will only be successful if all steps involved in it are optimized. Therefore, I deem it necessary to describe explicit and implicit flow solvers, unstructured multigrid methods, adaptive refinement schemes, grid generation and graphics in 3‐D, the effective use of supercomputer hardware and memory, as well as the combination of structured and unstructured grids.
Abstract
The current state of the art of Finite Element Methods in Computational Fluid Dynamics is reviewed. The aim of this review is to point out what appear currently as the [...]
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Finite Element Flux-Corrected Transport (FEM-FCT) for the Euler and Navier-Stokes equations
R. Lohner, K. Morgan, J. Peraire, M. Vahdati

International Journal for Numerical Methods in Fluids (1987). Vol. 7 (10), pp. 356-361

Abstract
A high resolution finite element method for the solution of problems involving high speed compressible flows is presented. The method uses the concepts of flux-corrected transport and is presented in a form which is suitable for implementation on completely unstructured triangular or tetrahedral meshes. Transient and steady state examples are solved to illustrate the performance of the algorithm.
Abstract
A high resolution finite element method for the solution of problems involving high speed compressible flows is presented. The method uses the concepts of flux-corrected transport [...]
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Some useful data structure for generation of unstructured grid
R. Lohner

Communications in numerical methods in engineering (1988). Vol. 4 (1), pp. 123-135

Abstract
Several data structures for the generation of unstructured grids are described. Their usefulness stems from the fact that they enable the necessary search operations to be performed in an optimal way. In particular, we describe heap lists, quad- and octrees, and linked lists. Combining these data structures, the important problem of interpolating information between unstructured grids is also solved.
Abstract
Several data structures for the generation of unstructured grids are described. Their usefulness stems from the fact that they enable the necessary search operations to be [...]
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Numerical simulation of shock-box interaction using an adaptive shock capturing scheme
J. Baum, R. Lohner

AIAA Journal (1988). Vol. 32 (4), pp. 682-690

Abstract
A recently developed transient, two-dimensional, finite-element shock capturing scheme is applied to the study of shock interaction with a box suspended above a rigid surface. The results demonstrate the excellent resolution of the captured shocks and the application of a newly developed adaptive refinement/coarsening algorithm. In addition to interesting shock propagation and interaction processes, the results demonstrate the capability of the new code to capture, and define in great detail, vortices shed from the downstream corners of the box. The ability of the new scheme to model such fluid dynamic phenomena as shock-shock, shock-surface, and shock-vortex interactions, as well as vortex dynamics, are demonstrated.
Abstract
A recently developed transient, two-dimensional, finite-element shock capturing scheme is applied to the study of shock interaction with a box suspended above a rigid surface. [...]
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Adaptive Finite Element Flux Corrected Transport Techniques for CFD
K. Morgan, J. Peraire, R. Lohner

(1988). Finite Elements. ICASE/NASA LaRC Series. Springer, New York, NY

Abstract
In previous papers [1,2] we have described an explicit finite element solution procedure for the compressible Euler and Navier-Stokes equations. The approach was a finite element equivalent of a two-step Lax-Wendroff scheme and was implemented on unstructured triangular or tetrahedral grids. An important feature of the work was the use of adaptive mesh refinement methods for the solution of steady state problems in two dimensions, using error indicators based upon interpolation theory.
Abstract
In previous papers [1,2] we have described an explicit finite element solution procedure for the compressible Euler and Navier-Stokes equations. The approach was a finite [...]
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Generation of three-dimensional unstructured grids by the advancing-front method
R. Lohner, P. Parikh

International Journal for Numerical Methods in Fluids (1988). Vol. 8 (10), pp. 1135-1149

Abstract
The generation of three-dimensional unstructured grids using the advancing-front technique is described. This technique has been shown to be effective for the generation of unstructured grids in two dimensions.1,2 However, its extension to three-dimensional regions required algorithms to define the surface and suitable data structures that avoid excessive CPU-time overheads for the search operations involved. After obtaining an initial triangulation of the surfaces, tetrahedra are generated by successively deleting faces from the generation front. Details of the grid generation algorithm are given, together with examples and timings.
Abstract
The generation of three-dimensional unstructured grids using the advancing-front technique is described. This technique has been shown to be effective for the generation [...]
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An adaptive finite element solver for transient problems with moving bodies
R. Lohner

Computers and Structures (1988). Vol. 30 (1-2), pp. 303-317

Abstract
The combination of adaptive remeshing techniques, flow solvers for transient problems with moving grids, and integrators for rigid body motion is presented. The resulting scheme allows the economic simulation of fully coupled fluid-rigid body interaction problems of arbitrary geometric complexity. Several results are given to demonstrate the capabilities developed.
Abstract
The combination of adaptive remeshing techniques, flow solvers for transient problems with moving grids, and integrators for rigid body motion is presented. The resulting [...]
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FEM-FCT - Combining unstructured grids with high resolution
R. Lohner, K. Morgan, M. Vahdati, J. Boris, D. Book

Communications in numerical methods in engineering (1988). Vol. 4 (6), pp. 356-370

Abstract
We present the extension of flux‐corrected transport (FCT) schemes to unstructured grids. The spatial discretization is performed via finite elements. In particular, we have chosen triangular elements in two dimensions. The limiting procedure is based on Zalesak's extension to more than one dimension of the FCT schemes developed by Boris and Book. The resulting scheme, FEM‐FCT, is capable of resolving moving and stationary shocks within two elements, and several examples are given that demonstrate the accuracy attainable, even for complicated geometries.
Abstract
We present the extension of flux‐corrected transport (FCT) schemes to unstructured grids. The spatial discretization is performed via finite elements. In particular, [...]
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Adaptive remeshing for transient problems
R. Lohner

Computer Methods in Applied Mechanics and Engineering (1989). Vol. 75 (1-3), pp. 195-214

Abstract
Adaptive remeshing schemes for transient problems are presented. The main advantage of these schemes is the ease in incorporating directional refinement and body motion in the context of adaptive refinement. Practical numerical examples for the Euler equations, run on the CRAY-XMP-24 at NRL, show that the adaptive remeshing scheme by itself cannot compete with ordinary h-refinement for strongly unsteady flows that require a grid change every 5–10 timesteps. Therefore, we study the combination of adaptive remeshing and h-refinement. After generating a coarser grid with stretched elements, the whole grid is h-refined at once. Even with one level of h-refinement, the combined scheme easily out-performs ordinary h-refinement, yielding a very effective adaptive refinement method for this class of problems.
Abstract
Adaptive remeshing schemes for transient problems are presented. The main advantage of these schemes is the ease in incorporating directional refinement and body motion [...]
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A vectorized particle tracer for unstructured grids
R. Lohner, J. Ambrosiano

Journal of Computational Physics (1990). Vol. 91 (1), pp. 22-31

Abstract
A vectorized particle tracer for unstructured grids is described. The basic approach is to use elementary properties of the linear basis functions to search for particles on the grid using the element last occupied as an initial guess. To permit vectorization, a simple binary sort of the particles is performed every timestep such that all particles that have as yet not found their host element remain at the top of the list. In this way, vector-loops can be easily formed. Timings taken from a numerical example indicate that speed-ups of the order of 1:14 can be obtained on vector-machines when using this algorithm.
Abstract
A vectorized particle tracer for unstructured grids is described. The basic approach is to use elementary properties of the linear basis functions to search for particles [...]
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Numerical simulation of shock interaction with complex geometry canisters
J. Baum, E. Loth, R. Lohner

(1990). AIP Conference Proceedings, vol. 209

Abstract
The objective of this research is to investigate shock interaction with complex geometry canisters suspended above a rigid elevated surface. Several geometries were examined in an effort to reduce the loads on the canisters during the shock diffraction phase. A new transient, two‐dimensional, finite‐element shock capturing scheme was utilized. Excellent shock resolution was demonstrated, as well as the efficiency of the newly developed adaptive refinement/coarsening algorithm. In addition to interesting shock wave propagation and interaction processes, the results demonstrated the capability of the new code to capture, and define in great detail, vortices shed from the downstream side of the canister.
Abstract
The objective of this research is to investigate shock interaction with complex geometry canisters suspended above a rigid elevated [...]
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Three-dimensional fluid-structure interaction using a finite element solver and adaptive remeshing
R. Lohner

Computing Systems in Engineering (1990). Vol. 1 (2), pp. 257-272

Abstract
The combination of adaptive remeshing techniques, flow solvers for transient problems with moving grids, and consistent rigid body motion integrators in three dimensions is presented. The resulting scheme allows the economical simulation of fully coupled fluid-rigid body interaction problems of arbitrary geometric complexity. Several results, showing three-dimensional store separation, are given to demonstrate the capabilities developed.
Abstract
The combination of adaptive remeshing techniques, flow solvers for transient problems with moving grids, and consistent rigid body motion integrators in three dimensions is [...]
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Electromagnetic PIC simulations using finite elements on unstructured grids
J. Ambrosiano, S. Brandon, R. Lohner

(1991). Proceeding 14th Conference on Numerical Simulation of Plasmas, Annapolis

Abstract
There is an increasing demand to use kinetic plasma simulations to model real plasma devices such as e-beam diodes, plasma torches, opening switches, and so on. With this demands comes the realization that standard simulation tools based on rectangular structured meshes are often too inflexible to accommodate real device geometries. To gain geometric flexibility, one typically must abandon structured rectangular meshes. Some have had considerable success by distorting the grid to conform to boundary-fitted curvilinear coordinates. This gives substantial flexibility while retaining a logically rectangular data structure. However, to achieve the greatest flexibility, an unstructured mesh is necessary. For the last several years, we have been engaged in designing electromagnetic particle-in-cell (PIC) simulations that can be performed on unstructured grids of triangles. We feel this is a powerful strategy for matching kinetic plasma simulations to real problem geometries. Unstructured meshes not only accommodate complicated boundary shapes with ease, but also allow extreme local refinement without affecting resolution elsewhere. The basic challenges to overcome in formulating EM-PIC on these new meshes are: (1) grid generation; (2) particle interpolation and tracking, and (3) field solution. In this paper we briefly describe our techniques and give a simple example.
Abstract
There is an increasing demand to use kinetic plasma simulations to model real plasma devices such as e-beam diodes, plasma torches, opening switches, and so on. With this [...]
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Simple Elements and Linelets for Incompressible Flows
R. Lohner

(1991). The finite element method in the 1990’s. Springer, Berlin, Heidelberg

Abstract
The current trends for the simulation of large-scale incompressible flow fields using finite elements are discussed. The main items are: a) the use of simple elements through stabilization and analogy with LBB-satisfying elements, and b) the development of fast solvers for general grids.
Abstract
The current trends for the simulation of large-scale incompressible flow fields using finite elements are discussed. The main items are: a) the use of simple elements through [...]
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Three-dimensional space-marching algorithm on unstructured grids
M. McGrory, R. Lohner, R. Walters

AIAA Journal (1991). Vol. 29 (1), pp. 1844-1849

Abstract
A three-dimensional space-marching algorithm using an unstructured discretization is proposed. The method utilizes a two-dimensional unstructured grid generator to construct grids in a crossflow plane while maintaining structure in the marching direction. The spatial discretization is obtained by applying a characteristic-based, upwind, finite volume scheme for the solution of the Euler equations. Solutions are presented for several different geometries comparing the results with existing numerical techniques and experiment.
Abstract
A three-dimensional space-marching algorithm using an unstructured discretization is proposed. The method utilizes a two-dimensional unstructured grid generator to construct [...]
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Formation of shocks within axisymmetric nozzles
E. Loth, J. Baum, R. Lohner

AIAA Journal (1992). Vol. 30 (1), pp. 268-270

Abstract
The formation of shocks within axisymmetric supersonic nozzles has received considerable attention in the past, both experimentally and computationally. The presence of undesirable oblique shocks can significantly alter the downstream flowfield, reduce the thrust efficiency, and affect both the external acoustic signature and base pressure. In this paper numerical simulations of axisymmetric supersonic nozzle flow have been accomplished using an axisymmetric version of the finite element method/flux corrected transport algorithm. The adaptive unstructured gridding and the conservative nonlinear FCT scheme predicted shock formation that agreed with experimental data.
Abstract
The formation of shocks within axisymmetric supersonic nozzles has received considerable attention in the past, both experimentally and computationally. The presence of undesirable [...]
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Parallel unstructured grid generation
R. Lohner, J. Camberos, M. Merriam

Computer Methods in Applied Mechanics and Engineering (1992). Vol. 95 (3), pp. 343-357

Abstract
A parallel unstructured grid generation algorithm is presented and implemented on the INTEL hypercube. Different processor hierarchies are discussed, and the appropriate hierarchies for mesh generation and mesh smoothing are selected. A domain-splitting algorithm for unstructured grids, which tries to minimize the surface-to-volume ratio of each subdomain, is described. This splitting algorithm is employed both for grid generation and grid smoothing. Results obtained on the INTEL hypercube demonstrate the effectiveness of the algorithms developed.
Abstract
A parallel unstructured grid generation algorithm is presented and implemented on the INTEL hypercube. Different processor hierarchies are discussed, and the appropriate hierarchies [...]
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Vorticity produced by shock wave diffraction
S. Siver, E. Loth, J. Baum, R. Lohner

Shock Waves (1992). Vol. 2, pp. 31-41

Abstract
Numerical simulations with a monotonicity preserving flow solver have been performed to study shock diffraction phenomena and shock wave generated vorticity. The computations were performed using the conservative Finite Element Method-Flux Corrected Transport (FEM-FCT) scheme, which has been shown to have an excellent predictive capability for various compressible flows with both strong and weak shocks. An adaptive unstructured methodology based on adapting to high density and entropy gradients was used in conjunction with a conservative shock-capturing scheme to adequately resolve strong and weak flowfield gradients. The chief interest was the formation of vorticity arising from shock wave propagation over a sharp corner and the high accuracy and resolution of the interacting compressible wave features. Numerical simulations were compared with previous experimental results and exhibited remarkably good agreement in terms of compressible wave propagation, as well as vorticity development and transport. The computations also allowed insight into the fundamental fluid dynamics, specifically shock diffraction, vortex convection and shock-vortex interactions.
Abstract
Numerical simulations with a monotonicity preserving flow solver have been performed to study shock diffraction phenomena and shock wave generated vorticity. The computations [...]
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Finite element methods in CFD: Grid generation, adaptivity, and parallelization
R. Lohner

(1992). Special Course on Unstructured Grid Methods for Advection Dominated Flows

Abstract
Numerical methods for the solution of field problems using unstructured grids have reached a high degree of maturity. Although computational fluid dynamics (CFD) have been dominated by structured grids, with the increase in computational ability, unstructured grids have started to have an impact on complex geometrical problems in CFD. The following paper describes grid generation, adaptive refinement schemes, visualization and parallelization issues. It also includes a short chapter on CFD among related disciplines that will help the newcomer with flow simulation codes
Abstract
Numerical methods for the solution of field problems using unstructured grids have reached a high degree of maturity. Although computational fluid dynamics (CFD) have been [...]
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Supersonic Flow over an Axisymmetric Backward-Facing Step
E. Loth, K. Kailasanth, R. Lohner

Journal of Spacecraft and Rockets (1992). Vol. 29 (3), pp. 352-359

Abstract
Large eddy numerical simulations of supersonic flows over an axisymmetric backward-facing step have been completed using a recently developed axisymmetric version of the finite element method-flux corrected transport algorithm, FEM-FCT. The code is based on the mixing layer and recompression premises of the Chapman-Korst model. It solves the time-accurate Euler equations utilizing 1) adaptive unstructured gridding to resolve flow feature details and 2) a conservative nonlinear scheme to capture features in the compressible flowfield. This approach may be employed since the location of the separation point is fixed at the sharp corner. The simulation allows the large-scale structures present in the mixing layer to interact dynamically with the recompression region. Comparisons have been made with available experimental data for a range of Mach numbers and step height to step radius ratios for which boundary-layer effects are not pronounced. In general, good agreement between predictions and measurements was found for 1) the time-averaged surface pressure distributions along the backstep and the reattachment wall, 2) the flowfield structure in general, and 3) the downstream reattachment lengths. Effects of axisymmetry were noted in flowfield characteristics such as increased base pressure, curvature of expansion fans, stronger recompression shocks, and higher Mach number levels in the subsonic recirculating region.
Abstract
Large eddy numerical simulations of supersonic flows over an axisymmetric backward-facing step have been completed using a recently developed axisymmetric version of the finite [...]
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Adaptive h‐refinement on 3D unstructured grids for transient problems
R. Lohner, J. Baum

International Journal for Numerical Methods in Fluids (1992). Vol. 14 (12), pp. 1407-1419

Abstract
An adaptive finite element scheme for transient problems is presented. The classic h‐enrichment/coarsening is employed in conjunction with a tetrahedral finite element discretization in three dimensions. A mesh change is performed every n time steps, depending on the Courant number employed and the number of ‘protective layers’ added ahead of the refined region. In order to simplify the refinement/coarsening logic and to be as fast as possible, only one level of refinement/coarsening is allowed per mesh change. A high degree of vectorizability has been achieved by pre‐sorting the elements and then performing the refinement/coarsening groupwise according to the case at hand. Further reductions in CPU requirements arc realized by optimizing the identification and sorting of elements for refinement and deletion. The developed technology has been used extensively for shock‐shock and shock‐object interaction runs in a production mode. A typical example of this class of problems is given.
Abstract
An adaptive finite element scheme for transient problems is presented. The classic h‐enrichment/coarsening is employed in conjunction with a tetrahedral finite element [...]
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Eulerian-Eulerian and Eulerian-Lagrangian methods in two phase flow
S. Siver, E. Loth, J. Baum, R. Lohner

(1993). Thirteenth International Conference on Numerical Methods in Fluid Dynamics. Lecture Notes in Physics, vol 414. Springer, Berlin, Heidelberg

Abstract
This paper describes a Finite Element Method - Flux Corrected Transport (FEM-FCT) approach with an unstructured adaptive grid scheme to the simulation of two-phase flow. The gas equations are computed using an Eulerian frame of reference, while the particle transport is computed using both Eulerian and Lagrangian frames of reference. One dimensional shock wave attenuation was investigated to evaluate the performance of these methodologies and the gas-solid interphase transport models
Abstract
This paper describes a Finite Element Method - Flux Corrected Transport (FEM-FCT) approach with an unstructured adaptive grid scheme to the simulation of two-phase flow. The [...]
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An implicit three-dimensional finite element solver for unstructured meshes
H. Luo, J. Baum, R. Lohner, J. Cabello

AIAA Journal (1993). Vol. 11 (2), pp. 1027-1028

Abstract
The development of an implicit 3D finite element algorithm for the solution of the compressible Euler and Navier-Stokes equations on unstructured meshes is reported. Numerical results for both inviscid and viscous flows are presented to demonstrate the proposed scheme's performance. The treatment of boundary conditions is found to be vital to the success of an implicit scheme
Abstract
The development of an implicit 3D finite element algorithm for the solution of the compressible Euler and Navier-Stokes equations on unstructured meshes is reported. [...]
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Some useful renumbering strategies for unstructured grids
R. Lohner

International Journal for Numerical Methods in Engineering (1993). Vol. 36 (19), pp. 3259-3270

Abstract
Several renumbering strategies for unstructured grids are discussed. They lead to a minimization of eache-misses and an optimal grouping of elements for different computer platforms, from superscalar workstations to multiprocessor register-to-register vector machines. Timings for a typical computational fluid dynamics (CFD) code that employs these renumbering strategies indicate that CPU requirements may be halved by applying them. The renumbering strategies discussed are all of linear time complexity, making them ideally suited for applications requiring frequent mesh changes. Furthermore, these renumbering strategies are not only valid for element-based codes but carry over to edge-based or face-based field solvers
Abstract
Several renumbering strategies for unstructured grids are discussed. They lead to a minimization of eache-misses and an optimal grouping of elements for different computer [...]
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Three‐dimensional parallel unstructured grid generation
A. Shostko, R. Lohner

International Journal for Numerical Methods in Engineering (1994). Vol. 38 (6), pp. 905-925

Abstract
An algorithm for the parallel generation of 3-D unstructured grids is presented. The technique is an extension of the algorithm presented in Reference 21 for the 2-D case. The method uses a background grid as the means to separate spatially different regions, enabling the concurrent, parallel generation of elements in different domains and interdomain regions. The parallel 3-D grid generator was implemented and tested on the INTEL hypercube and Touchstone Delta parallel computers. The results obtained demonstrate the effectiveness of the algorithm developed. The methodology is applicable to the parallel implementation of a wide range of problems that are, in principle, scalar by nature, and do not lend themselves to SIMD parallelization.
Abstract
An algorithm for the parallel generation of 3-D unstructured grids is presented. The technique is an extension of the algorithm presented in Reference 21 for the 2-D case. [...]
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Electromagnetics via the Taylor-Galerkin Finite Element Method on Unstructured Grids
J. Ambrosiano, S. Brandon, R. Lohner, R. DeVore

Journal of Computational Physics (1994). Vol. 110 (2), pp. 310-319

Abstract
Traditional techniques for computing electromagnetic solutions in the time domain rely on finite differences. These so-called finite-difference time-domain (FDTD) methods are usually defined only on regular lattices of points and can be too restrictive for geometrically demanding problems. Great geometric flexibility can be achieved by abandoning the regular latticework of sample points and adopting an unstructured grid. An unstructured grid allows one to place the grid points anywhere one chooses, so that curved boundaries can be fit with ease and local regions in which the field gradients are steep can be selectively resolved with a fine mesh. In this paper we present a technique for solving Maxwell's equations on an unstructured grid based on the Taylor-Galerkin finite-element method. We present several numerical examples which reveal the fundamental accuracy and adaptability of the method. Although our examples are in two dimensions, the techniques and results generalize readily to 3D.
Abstract
Traditional techniques for computing electromagnetic solutions in the time domain rely on finite differences. These so-called finite-difference time-domain (FDTD) methods [...]
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Numerical simulation of shock-box interaction using an adaptive finite element scheme
J. Baum, R. Lohner

AIAA Journal (1994). Vol. 32 (4), pp. 682-692

Abstract
A transient two-dimensional, finite elemnt shock capturing scheme on unstructured grids was applied to the study of a shock interacting with a box suspended above a rigid elevated surface. The area between the box and the surface was partially blocked by the box support beams, resulting in complex shock diffraction processes. The results demonstrate the capability of the developed adaptive refinement/corsening algorithm to properly adapt to weak shocks, expansions, and contact discontinuities, and highlight the resulting excellent resolution of the captured flow features. In addition to interesting shock diffraction and propagation phenomena, the results demonstrate the capability of the new code to capture, and define in great detail, vortex sheets shed from sharp corners. We show that the baroclinic effect, an inviscid process, controls the shedding phenomenon during the diffraction phase. Hence, the Eulerian model is able to correctly predict the process.
Abstract
A transient two-dimensional, finite elemnt shock capturing scheme on unstructured grids was applied to the study of a shock interacting with a box suspended above a rigid [...]
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Edge-based element scheme for the Euler equations
H. Luo, J. Baum, R. Lohner

AIAA Journal (1994). Vol. 32 (6), pp. 1182-1190

Abstract
This paper describes the development, validation, and application of a new finite element scheme for the solution of the compressible Euler equations on unstructured grids. The implementation of the numerical scheme is based on an edge-based data structure, as opposed to a more element-based data structure. The use of this edge-based data structure not only improves the efficiency of the algorithm but also enables a straightforward implementation of the upwind schemes in the context of finite element methods. The algorithm has been tested and validated on some well documented configurations. A flow solution about a complete F-18 fighter is shown to demonstrate the accuracy and robustness of the proposed algorithm.
Abstract
This paper describes the development, validation, and application of a new finite element scheme for the solution of the compressible Euler equations on unstructured grids. [...]
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Unstructured Adaptive Remeshing Finite Element Method for Dusty Shock Flows
S. Siver, E. Loth, J. Baum, R. Lohner

Shock Waves (1994). Vol. 4 (1), pp. 15-23

Abstract
The passage of planar shocks in a dusty gas was investigated to note effects due to particle loading and initial shock Mach number. Two-phase flow equations have been added to a conservative, monotonic flow solver to allow study of compressible particle and droplet flows, which are of importance for shock propagation in two-phase flows and spray propulsion systems. The formulation developed herein employed a conservative Eulerian treatment for the gas and particle phases. The computations were performed using the finite element method-flux corrected transport (FEM-FCT) scheme, which has shown excellent predictive capability of various compressible flows which include both strong and weak shocks. The flux limiting technique was modified to provide monotonic particle velocity fields to increase the scheme's computational stability. Adaptive unstructured methodology based on adapting to high gradients of both the fluid and particle densities was used in conjunction with the conservative shock-capturing scheme to adequately resolve strong flowfield gradients. The shock attenuation of this scheme was then compared with previous experimental and numerical results and was found to yield robust predictions. Various interphase coupling terms were also considered to note their effect on the shock attenuation.
Abstract
The passage of planar shocks in a dusty gas was investigated to note effects due to particle loading and initial shock Mach number. Two-phase flow equations have been added [...]
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Ray tracing with a space‐filling finite element mesh
J. Fave, R. Lohner

International Journal for Numerical Methods in Engineering (1994). Vol. 37 (20), pp. 3571-3580

Abstract
A new ray‐tracing technique is presented which does not work with ray–object intersections per se , but is based on the traversal of an unstructured tetrahedral mesh providing a convex enclosure of a scene of polyhedral objects. The tetrahedral mesh provides tight bounding and an adaptive subdivision of space. This non‐hierarchical data structure is traversed adaptively until one is led directly and unconditionally to the first object intersected. Rendering times are directly related to the average thickness of the enclosing mesh since all tetrahedra are traversed in constant time. Since the proposed algorithm operates directly with volume elements, it allows for volumetric rendering effects. Volume rendering or anisotropic media can be implemented without any further effort. This is an important advantage as compared to usual techniques, which only operate on surface data. Timings for several examples show that the use of this type of ray‐tracing technique, which is more suitable for general purpose visualization codes than traditional techniques, results in CPU times that are comparable with the best ray‐tracing techniques presently used. This is an unexpected and important result, as the vectorization and parallclization of the proposed technique are straightforward, in contrast with traditional ray‐tracing techniques
Abstract
A new ray‐tracing technique is presented which does not work with ray–object intersections per se , but is based on the traversal of an unstructured tetrahedral [...]
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Edges, stars, superedges and chains
R. Lohner

Computer Methods in Applied Mechanics and Engineering (1994). Vol. 111 (3-4), pp. 255-263

Abstract
Several possibilities for the reduction of indirect addressing operations within edge-based solvers are discussed. It is shown that indirect addressing operations may be reduced by a factor in excess of 1 : 4 if edges are grouped and linked together. Tests of benchmark loops on two common engineering computer platforms reveal that CPU saving factors ranging from 1.3 to 3.5 may be realized when switching from edge-based to superedge or chain-based loops.
Abstract
Several possibilities for the reduction of indirect addressing operations within edge-based solvers are discussed. It is shown that indirect addressing operations may be reduced [...]
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Transient and steady heat conduction using an adaptive finite element cad-based approach
R. Lohner, J. McAnally

International Journal for Numerical Methods for Heat and Fluid Flow (1994). Vol. 4 (4), pp. 311-327

Abstract
A new heat transfer simulation capability is described. Non-traditional features of this capability include: a seamless link to CAD-CAM for rapid problem specification/description, integrated automatic grid generator tools for rapid mesh generation, nonlinear and/or varying material properties, source-terms and boundary conditions, a one-element type approach for simplicity and efficiency, automatic self-adaptive mesh refinement and coarsening with accurate error estimation, heavy reliance on iterative solvers, and on-line display on workstations for immediate visualization and user feedback. These innovations are documented on several examples that demonstrate the usefulness of the developed capability.
Abstract
A new heat transfer simulation capability is described. Non-traditional features of this capability include: a seamless link to CAD-CAM for rapid problem specification/description, [...]
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A Comparison Study of Two Finite-Element Schemes for Computation of Shock Waves
H. Luo, J. Baum, R. Lohner

(1995). Shock Waves @ Marseille I. Springer, Berlin, Heidelberg

Abstract
This paper describes an extensive comparison study of two high-order-accuracy finite-element schemes: one of upwind type, the other of flux-corrected transport type, for the simulation of shock wave propagation on unstructured meshes. The performance of these two schemes for the solution of the Euler equations on unstructured meshes is compared on the basis of solution accuracy and computational efficiency for some well-known test cases. Advantages and disadvantages of the two schemes are discussed.
Abstract
This paper describes an extensive comparison study of two high-order-accuracy finite-element schemes: one of upwind type, the other of flux-corrected transport type, for the [...]
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Mesh adaptation in fluid mechanics
R. Lohner

Engineering Fracture Mechanics (1995). Vol. 50 (5-6), pp. 819-847

Abstract
The development, application and impact of mesh adaptation procedures in the field of computational fluid mechanics (CFD) are reviewed. The discussion is restricted to unstructured (i.e. unordered) grids, such as those commonly encountered in finite element applications.
Abstract
The development, application and impact of mesh adaptation procedures in the field of computational fluid mechanics (CFD) are reviewed. The discussion is restricted to unstructured [...]
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Finite element simulation of a turbulent MHD system: comparison to a pseudo-spectral simulation
R. Frainchtein, S. Zalesak, R. Lohner, D. Spicer

Computer Physics Communications (1995). Vol. 86 (1-2), pp. 25-39

Abstract
A finite element MHD algorithm is used to simulate a two-dimensional, viscous and resistive turbulent model, namely the Orszag-Tang vortex. The results are compared to a pseudo-spectral simulation of the same system reported by Dahlburg and Picone (Phys. Fluids B 1 (1989) 2153). The agreement of results from both methods supports the contention that the finite element method can appropriately simulate systems exhibiting turbulence, thus enabling the use of realistic geometries and boundary conditions, as well as adaptive refinement on simulations of turbulent systems. A short discussion on the behavior of ▿·B is presented. An inverse correlation between spatial resolution and the magnitude of ▿·B was found. The relevance of our findings to Adaptive Mesh Refinement is briefly discussed.
Abstract
A finite element MHD algorithm is used to simulate a two-dimensional, viscous and resistive turbulent model, namely the Orszag-Tang vortex. The results are compared [...]
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Robust, Vectorized Search Algorithms for Interpolation on Unstructured Grids
R. Lohner

Journal of Computational Physics (1995). Vol. 118 (2), pp. 380-387

Abstract
Several search algorithms for the interpolation of data associated with unstructured grids are reviewed and compared. Particular emphasis is placed on the pitfalls these algorithms may experience for grids commonly encountered and on ways to improve their performance. It is shown how the most CPU-intensive portions of the search process may be vectorized. A technique for the proper interpolation of volumetric regions separated by thin surfaces is included. Timings for several problems show that speedups in excess of 1:5 can be obtained if due care is used when designing interpolation algorithms.
Abstract
Several search algorithms for the interpolation of data associated with unstructured grids are reviewed and compared. Particular emphasis is [...]
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Simulation of complex incompressible flows using a finite element solver on MIMD machines
R. Ramamurti, R. Lohner

(1995). Parallel Computational Fluid Dynamics 1993, New Trends and Advances, pp. 443-450

Abstract
An incompressible flow solver based on unstructured grids is implemented on parallel distributed-memory computer architecture. An important phase in the flow solver is the solution of the elliptic equations for the velocities and pressures. This elliptic solver is parallelized and incorporated into both the explicit and implicit versions of the incompressible flow solver. Performance and scalability studies are carried out on both Intel iPSC 860 and the Intel Delta prototype and show that the code is scalable. A parallelizable load balancing algorithm is developed to be used in conjunction with the incompressible flow solver. Steady and unsteady flows over a tri-element airfoil and NACA0012airfoil are computed using the parallel incompressible flow solver. The parallel flow solver is extended to 3D for simulation of flow past a fully appended submarine. The chapter concludes that the future developments will be focused on the incorporation of adaptive regridding in 2D and the parallel implementation of 3-D incompressible flow solver.
Abstract
An incompressible flow solver based on unstructured grids is implemented on parallel distributed-memory computer architecture. An important phase in the flow solver [...]
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Computation of the unsteady flow past a tuna with caudal fin oscillation
R. Ramamurti, R. Lohner, W. Sandberg

Transactions on Engineering Science (1996). Vol. 9, pp. 169-178

Abstract
Only recently has a capability for computing three-dimensional, unsteady incompressible flow over a changing geometry become available. In that work, the flow field generated during a torpedo launch from a submarine was computed. This paper describes the extension of that work to carry out a direct computation, making no geometric simplifications, of the unsteady flow past a tuna, including the oscillatory caudal fin motion. In particular, described is the computation of the time variation of the pressure distribution over the entire body and the integration over all surfaces to obtain the unsteady thrust.
Abstract
Only recently has a capability for computing three-dimensional, unsteady incompressible flow over a changing geometry become available. In that work, the flow field generated [...]
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Large-Scale Blast Simulations
J. Baum, H. Luo, R. Lohner

(1996). Computation of Three-Dimensional Complex Flows. Notes on Numerical Fluid Mechanics (NNFM), vol 49. Vieweg+Teubner Verlag

Abstract
This paper describes the application of FEFL096, a three-dimensional, adaptive, finite element, edge-based, ALE shock capturing methodology on unstructured tetrahedral grids, to large-scale simulations of blast wave interaction with structures. The first simulation applied the CFD methodology to the numerical simulation of blast wave diffraction within the B-2 level of the World Trade Center garage. This simulation modeled blast wave diffraction about hundreds of rigidly-modeled structures, spread over a large area. The second simulation applied a new loose-coupling algorithm that combined FEFL096 and DYNA3D, a state-of-the-art Computational Structural Dynamics (CSD) methodology, to the simulation of shock interaction with a structurally-responding truck.
Abstract
This paper describes the application of FEFL096, a three-dimensional, adaptive, finite element, edge-based, ALE shock capturing methodology [...]
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A parallel implicit incompressible flow solver using unstructured meshes
R. Ramamurti, R. Lohner

Computers and Fluids (1996). Vol. 25 (2), pp. 119-132

Abstract
An incompressible flow solver based on unstructured grids is implemented on a parallel distributed memory computer architecture. An important phase in the flow solver is the solution of the elliptic equations for the velocities and pressure. This elliptic solver is parallelized and incorporated into both the explicit and implicit versions of the incompressible flow solver. Performance and scalability studies are carried out on both Intel iPSC 860 and the Intel Delta prototype, and these studies show that the code is scalable. A parallelizable load balancing algorithm is developed to be used in conjunction with the incompressible flow solver. Steady and unsteady flows over a tri-element airfoil and NACA0012 airfoil are computed using the parallel incompressible flow solver.
Abstract
An incompressible flow solver based on unstructured grids is implemented on a parallel distributed memory computer architecture. An important [...]
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Dusty shock flow with unstructured adaptive finite elements and parcels
S. Siver, E. Loth, J. Baum, R. Lohner

AIAA Journal (1996). Vol. 34 (5), pp. 1078-1080

Abstract
Our objective is to formulate and develop an Eulerian-Lagrangian (E-L) method with an adaptive grid FEM-FCT flow solver that is computationally efficient. This method is used to predict a particle laden shock wave attenuation as a test case and to compare performance characteristics (computation speed, memory, and accuracy) with an E-E implentation that also includes adaptive unstructured grids
Abstract
Our objective is to formulate and develop an Eulerian-Lagrangian (E-L) method with an adaptive grid FEM-FCT flow solver that is computationally efficient. This method is used [...]
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Regridding Surface Triangulations
R. Lohner

Journal of Computational Physics (1996). Vol. 126 (1), pp. 1-10

Abstract
An advancing front surface gridding technique that operates on discretely defined surfaces (i.e. triangulations) is presented. Different aspects that are required to make the procedure reliable for complex geometries are discussed. Notable among these are (a) the recovery of surface features and discrete surface patches from the discrete data, (b) filtering based on point and side-normals to remove undesirable data close to cusps and corners, (c) the proper choice of host faces for ridges, and (d) fast interpolation procedures suitable for complex geometries. Post-generation surface recovery or repositioning techniques are discussed. Several examples ranging from academic to industrial demonstrate the utility of the proposed procedure forab initiosurface meshing from discrete data, such as those encountered when the surface description is already given as discrete, the improvement of existing surface triangulations, as well as remeshing applications during runs exhibiting significant change of domain.
Abstract
An advancing front surface gridding technique that operates on discretely defined surfaces (i.e. triangulations) is presented. Different aspects [...]
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Progress in grid generation via the advancing front technique
R. Lohner

Engineering with Computers (1996). Vol. 12, pp. 186-210

Abstract
We describe recent extensions and improvements to the advancing front grid generation technique. These improvements target a range of applicability, speed and user friendliness. The range of applicability is enlarged by the ability to produce volumetric grids around thin surfaces (such as shells, membranes, fabrics or surfaces with cusps), the generation of high aspect ratio grids for Navier-Stokes applications, the generation of higher order triangular and tetrahedral elements, and the generation of quadrilateral and hexahedral elements. Speed improvements are the result of reduced search overheads, as well as vectorization and parallelization. User friendliness is enhanced by the ability to grid directly discrete data and simpler ways of specifying the desired element size and shape in space. Numerous examples are included that demonstrate the versatility and maturity that advancing front grid generators have achieved.
Abstract
We describe recent extensions and improvements to the advancing front grid generation technique. These improvements target a range of applicability, speed and user friendliness. [...]
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Improved ALE mesh velocities for moving bodies
R. Lohner, C. Yang

Commun. Numer. Meth. Engng (1996). Vol. 12 (10), pp. 599-608

Abstract
A Laplacian smoothing of the mesh velocities with variable diffusivity based on the distance from moving bodies is introduced. This variable diffusivity enforces a more uniform mesh velocity in the region close to the moving bodies. Given that in most applications these are regions where small elements are located, the new procedure decreases element distortion considerably, reducing the need for local or global remeshing, and in some cases avoiding it altogether.
Abstract
A Laplacian smoothing of the mesh velocities with variable diffusivity based on the distance from moving bodies is introduced. This variable diffusivity enforces a more uniform [...]
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Extensions and improvements of the advancing front grid generation technique
R. Lohner

Comput. Methods Appl. Mech. Engrg., (1996). Vol. 5 (10), pp. 119-132

Abstract
We describe extensions and improvements to the advancing front grid generation technique that have proven useful over the years. The following areas are treated in detail: situations with thin or crossing surfaces, meshing of surfaces defined by triangulations, and ease of user input to define the desired element size in space. The first extension is important if one considers the generation of volumetric grids around shells, membranes, fabrics, or CAD-data that exhibit cusps. Traditional advancing front generators are likely to fail in these situations. We propose the introduction of a crossing environment variable attached to faces and points in order to filter out undesired or incorrect information during the grid generation process. The second extension is required for situations where the surfaces to be gridded are not defined analytically, but via a triangulation. Typical cases where such triangulations are used to define the domain are geophysical problems, climate modelling and medical problems. The third topic deals with the reduction of manual labour to specify element size in space. Sources, element size attached directly to CAD-data, and adaptive background grids are discussed. Adaptive background grids, in combination with surface deviation tolerances, are used to obtain surface triangulations that represent the geometry faithfully, and at the same time enable a smooth transition to volumetric meshes.
Abstract
We describe extensions and improvements to the advancing front grid generation technique that have proven useful over the years. The following areas are treated in detail: [...]
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Improved ALE mesh velocities for moving bodies
R. Lohner, C. Yang

Commun. Numer. Meth. Engng (1996). Vol. 12 (10), pp. 599-608

Abstract
A Laplacian smoothing of the mesh velocities with variable diffusivity based on the distance from moving bodies is introduced. This variable diffusivity enforces a more uniform mesh velocity in the region close to the moving bodies. Given that in most applications these are regions where small elements are located, the new procedure decreases element distortion considerably, reducing the need for local or global remeshing, and in some cases avoiding it altogether.
Abstract
A Laplacian smoothing of the mesh velocities with variable diffusivity based on the distance from moving bodies is introduced. This variable diffusivity enforces a more uniform [...]
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Simulation of the magnetosphere with a new three dimensional MHD code and adaptive mesh refinement: Preliminary results
D. Spicer, S. Zalesak, R. Lohner, S. Curtis

Advances in Space Research (1996). Vol. 18 (8), pp. 253-262

Abstract
We present the first results from a new unstructured mesh three dimensional finite element MHD code which uses dynamic solution-adaptive mesh refinement in a manner similar to our two dimensional finite element MHD code /31/. The problem being considered here is the interaction of the solar wind with the earth's magnetosphere, using a three-dimensional Cartesian approximation. Our results strongly indicate that such adaptive mesh techniques have the ability to resolve structures in the three dimensional MHD flow field that would otherwise be possible only with orders of magnitude greater cost and that are most likely beyond the capability of present supercomputers.
Abstract
We present the first results from a new unstructured mesh three dimensional finite element MHD code which uses dynamic solution-adaptive mesh refinement in a manner similar [...]
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Comparisons of Preconditioned Iterative Methods in the Implicit Unstructured Solver of Compressible Flow
M. Nagaoka, R. Lohner

Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers (1997). Vol. 63 (605), pp. 153-160

Abstract
Preconditioned iterative methods in an implicit unstructured grid solver of compressible flows are compared. The three-dimensional Euler and Navier-Stokes equations are discretized by the edge-based finite volume method. The artificial dissipation scheme for the inviscid numerical fluxes is developed for the unstructured grid from Jameson's scheme for the structured grid. The following methods are compared to the supersonic and transonic inviscid flows and subsonic viscous laminar and turbulent flows: the central difference methods with the scalar and matrix dissipation scheme and Roe's upwind method with the MUSCL scheme for the inviscid fluxes; the scalar and matrix dissipation method for the left-hand side operator in the implicit scheme; the ILU, DILU and SGS factorizations for the preconditioner; and GMRES and Bi-CGSTAB methods for the linear system solver. The results show that a combination of the matrix dissipation in the inviscid fluxes and the scalar dissipation in the left-hand side works better than the other *schemes. In the preconditioned iterative methods, a combination of DILU or SGS and the Bi-CGSTAB is recommended for the aspect of required memory.
Abstract
Preconditioned iterative methods in an implicit unstructured grid solver of compressible flows are compared. The three-dimensional Euler and Navier-Stokes equations are discretized [...]
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Automatic unstructured grid generators
R. Lohner

Finite Elements in Analysis and Design (1997). Vol. 25 (1-2), pp. 111-134

Abstract
A review of automatic unstructured grid generators is given. These types of grids have found widespread use in computational fluid dynamics, computational structural dynamics, computational electro-magnetics and computational thermodynamics. The following topics are treated: the methods most commonly used, the specification of desired element size/shape and surface definition/meshing. Finally, the use of automatic grid generators as an enabling technology for moving body simulations and adaptive remeshing techniques is discussed.
Abstract
A review of automatic unstructured grid generators is given. These types of grids have found widespread use in computational fluid dynamics, computational structural dynamics, [...]
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Conservative Load Projection and Tracking for Fluid-Structure Problems
J. Cebral

AIAA Journal (1997). Vol. 35 (4), pp. 687-692

Abstract
The loose coupling of computational fluid dynamics and computational structural dynamics solvers introduces some problems related to the information transfer between the codes. Some techniques developed to solve the problems of the load transfer and interface surface tracking are presented. The main criterion is to achieve conservation of total loads and total energy. The load projection scheme is based on Gaussian integration and fast interpolation algorithms for unstructured grids. The surface tracking algorithm, also based on interpolation, is important for many applications, including aeroelastic deformation of wings due to aerodynamic loads. The methodologies not only improve present fluid-structure interaction simulations, but also increase the range of their applicability. These techniques are of general character and can be used in other multidisciplinary applications as well.
Abstract
The loose coupling of computational fluid dynamics and computational structural dynamics solvers introduces some problems related to the information transfer between the codes. [...]
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On Some Outstanding Issues in CFD
R. Lohner

(1998). ICASE/LaRC Interdisciplinary Series in Science and Engineering. Vol 6, pp. 195-212. Springer, Dordrecht

Abstract
Against the general feeling that ‘CFD is solved’, I offer a few remarks from the trenches. When performing large-scale simulations of geometrically and physically complex flows, the notion of reliable, cost-effective, widely applicable and easy-to-use CFD still appears more as fiction than reality. The present monograph addresses some major areas where progress is urgently required. These areas are listed in the order a typical CFD run proceeds: model import/creation, grid generation, flow solvers, mesh adaptation and quality control. Finally, with a view towards the coming decade, code, data and project management are discussed.
Abstract
Against the general feeling that ‘CFD is solved’, I offer a few remarks from the trenches. When performing large-scale simulations of geometrically and physically [...]
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Parallelizing the construction of indirect access arrays for shared‐memory machines
J. Tuszynski, R. Lohner

Comput. Methods Appl. Mech. Engrg., (1998). Vol. 14 (8), pp. 773-781

Abstract
A way has been found to form indirect addressing lists in parallel on shared-memory parallel machines. The maximum possible speed-up for typical tetrahedral grids is approximately 1:23. The algorithm requires an additional scratch array to shift from the serial ‘elements surrounding points’ to the parallel ‘elements surrounding processors surrounding points’ paradigm. The algorithm developed is general in nature, i.e. applicable to all indirect addressing lists. All numerical methods requiring the construction of indirect data structures, such as sparse matrix linear algebra procedures, field and particle solvers operating on unstructured grids, and network flow applications should see a benefit from this algorithm when running on shared-memory parallel machines
Abstract
A way has been found to form indirect addressing lists in parallel on shared-memory parallel machines. The maximum possible speed-up for typical tetrahedral grids is approximately [...]
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Renumbering strategies for unstructured-grid solvers operating on shared-memory, cache-based parallel machines
R. Lohner

Comput. Methods Appl. Mech. Engrg., (1998). Vol. 163 (1-4), pp. 95-109

Abstract
Two renumbering strategies for field solvers based on unstructured grids that operate on shared-memory, cache-based parallel machines are described. Special attention is paid to the avoidance of cache-line overwrite, which can lead to drastic performance degradation on this type of machines. Both renumbering techniques avoid cache-misses and cache-line overwrite while allowing pipelining, leading to optimal coding for this type of hardware
Abstract
Two renumbering strategies for field solvers based on unstructured grids that operate on shared-memory, cache-based parallel machines are described. Special attention is paid [...]
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Generalized Meshing Environment for Computational Mechanics
L. Spradley, R. Lohner, T. Chung

AIAA Journal (1998). Vol. 36 (9), pp. 1735-1737

Abstract
One of the most time-consuming tasks in performing any discrete analysis the construction of a suitable mesh to represent the computational domain. Mesh generation today remains one of the pacing items in computational mechanics and consumes too many work hours and too many computers resources. This critical need for more progress in three-dimensional resources. This critical need for more progress in three-dimensional mesh generation certainly requires efficient geometry definition systems and advances in meshing methods. However, another major factor toward this progress is efficient methodology and computer software for automation of the meshing process. It is precisely this aspect of meshing that’s is the focus of this Note.
Abstract
One of the most time-consuming tasks in performing any discrete analysis the construction of a suitable mesh to represent the computational domain. Mesh generation today remains [...]
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Distributed visualization in computational fluid dynamics
J. Cebral, R. Lohner

(1998). Computational Fluid Dynamics Review 1998, Part 9, pp. 1097-1112

Abstract
The use of parallel computers and in particular distributed memory architectures imposes a number of requirements on the visualization systems for Computational Fluid Dynamics (CFD). We describe the design and capabilities of our distributed visualization software which can handle parallel multidisciplinary applications, can connect to a running solver for on-line display and steering, supports collaborative visualization and can be used as a tool for the automatic making of movies and animations. This discussion serves as an overview of the current trends and developments in visualization as applied to CFD and other computational sciences.
Abstract
The use of parallel computers and in particular distributed memory architectures imposes a number of requirements on the visualization systems for Computational Fluid Dynamics [...]
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Computation of the 3-D Unsteady Flow Past Deforming Geometries
R. Ramamurti, R. Lohner, W. Sandberg

Int. J. Computational Fluid Dynamics (1999). Vol. 13 (1), pp. 83-99

Abstract
A 3-D incompressible unsteady flow solver based on simple finite elements with adaptive remeshing and grid movement for both moving and deforming surfaces is described. We demonstrate the combination of adaptive remeshing techniques with the incompressible flow solver with the computation of flow past an eel in 2-D and a blue-fin tuna in 3-D. The flow past a swimming tuna was computed for two extreme cases of the caudal fin frequency and swimming speed. A grid refinement study was performed and a grid converged solution for the force produced by the caudal fin was obtained.
Abstract
A 3-D incompressible unsteady flow solver based on simple finite elements with adaptive remeshing and grid movement for both moving and deforming surfaces is described. We [...]
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Parallel Advancing Front Grid Generation
R. Lohner, J. Cebral

(1999). IMR

Abstract
A parallel advancing front scheme has been developed. The domain to be gridded is rst subdivided spatially using a relatively coarse octree. Boxes are then identiied and gridded in parallel. A scheme that resembles closely the advancing front technique on scalar machines is recovered by only considering the boxes of the active front that generate small elements. The procedure has been implemented on the SGI Origin class of machines using the shared memory paradigm. Timings for a variety of cases show speedups similar to those obtained for ow codes. The procedure has been used to generate grids in excess of a hundred million elements.
Abstract
A parallel advancing front scheme has been developed. The domain to be gridded is rst subdivided spatially using a relatively coarse octree. Boxes are then identiied and gridded [...]
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Surface triangulation over intersecting geometries
A. Shostko, R. Lohner, W. Sanderg

Int. J. Numer. Meth. Engng. (1999). Vol. 44 (9), pp. 1359-1376

Abstract
A method for the rapid construction of meshes over intersecting triangulated shapes is described. The method is based on an algorithm that automatically generates a surface mesh from intersecting triangulated surfaces by means of Boolean intersection/union operations. After the intersection of individual components is obtained, the exposed surface parts are extracted. The algorithm is intended for rapid interactive construction of non‐trivial surfaces in engineering design, manufacturing, visualization and molecular modelling applications. Techniques to make the method fast and general are described. The proposed algorithm is demonstrated on a number of examples, including intersections of multiple spheres, planes and general engineering shapes, as well as generation of surface and volume meshes around clusters of intersecting components followed by the computation of flow field parameters.
Abstract
A method for the rapid construction of meshes over intersecting triangulated shapes is described. The method is based on an algorithm that automatically generates a surface [...]
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The numerical simulation of strongly unsteady flow with hundreds of moving bodies
R. Lohner, C. Yang, J. Baum, H. Luo, D. Pelessone, C. Charman

Int. J. Numer. Meth. Fluids (1999). Vol. 31 (1), pp. 113-120

Abstract
A methodology for the simulation of strongly unsteady flows with hundreds of moving bodies has been developed. An unstructured grid, high-order, monotonicity preserving, ALE solver with automatic refinement and remeshing capabilities was enhanced by adding equations of state for high explosives, deactivation techniques and optimal data structures to minimize CPU overheads, automatic recovery of CAD data from discrete data, two new remeshing options, and a number of visualization tools for the preprocessing phase of large runs. The combination of these improvements has enabled the simulation of strongly unsteady flows with hundreds of moving bodies. Several examples demonstrate the effectiveness of the proposed methodology.
Abstract
A methodology for the simulation of strongly unsteady flows with hundreds of moving bodies has been developed. An unstructured grid, high-order, monotonicity preserving, ALE [...]
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A Navier-Stokes/Actuator Disc Simulation of Body-Ducted Propulsor Flow
C. Kiat Ho, R. Lohner, R. Ramamurti

(1999). American Physical Society, Division of Fluid Dynamics Meeting

Abstract
The interactions between a cylinder body and a ducted propeller is simulated using a coupled Navier-Stokes and actuator disc approach. The actuator disc approach raises the pressure of the fluid flowing through the propeller disc. Therefore, the finite number of blades, and the production of fluid rotation are ignored. An unstructured grid-based three-dimensional finite element method was used to solve the turbulent hydrodynamic flowfield. A Baldwin-Lomax turbulence model was used. The source strength was determined to match the thrust generated by propeller. The additional momentum due to the actuator disc is treated by a uniform distribution of sources over the propeller disc in momentum equation of Navier-Stokes equations. The three different momentum source strengths were used and the results from these cases and a no-source case are compared. It is shown that the source distribution can induce upstream separation if not properly chosen. (Work Sponsored by DoD HPCMO.)
Abstract
The interactions between a cylinder body and a ducted propeller is simulated using a coupled Navier-Stokes and actuator disc approach. The actuator disc approach raises the [...]
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Surface Gridding from Discrete Data
R. Lohner

(1995). Proceedings, 4th International Meshing Roundtable, Sandia National Laboratories, pp.29-44

Abstract
An advancing front gridding technique that operates on discretely defined surfaces is presented. Different aspects that are required to make the procedure reliable for complex geometries are discussed. Notable among these are: a) the recovery of surface features and discrete surface patches from the discrete data b) filtering based on point and side normals to remove undesirable data close to cusps and corners c) the proper choice of host faces for ridges d) fast interpolation procedures suitable for complex geometries. Post-generation surface recovery or repositioning techniques are discussed. Several examples ranging from academic to industrial demonstrate the utility of the proposed procedure for ab initio surface meshing from discrete data, such as those encountered when the surface description is already given as discrete, the improvement of existing surface triangulations, as well as remeshing applications during runs exhibiting significant change of domain.
Abstract
An advancing front gridding technique that operates on discretely defined surfaces is presented. Different aspects that are required to make the procedure reliable for complex [...]
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A Fast, Matrix-free Implicit Method for Computing Low Mach Number Flows on Unstructured Grids
H. Luo, J. Baum, R. Lohner

Int. J. Numer. Meth. Fluids (2000). Vol. 14 (2), pp. 133-157

Abstract
A fast, matrix-free implicit method has been developed to solve low Mach number flow problems on unstructured grids. The preconditioned compressible Euler and Navier-Stokes equations are integrated in time using a linearized implicit scheme. A newly developed fast, matrix-free implicit method, GMRES + LU−SGS, is then applied to solve the resultant system of linear equations. A variety of computations has been made for a wide range of flow conditions, for both in viscid and viscous flows, in both 2D and 3D to validate the developed method and to evaluate the effectiveness of the GMRES + LU−SGS method. The numerical results obtained indicate that the use of the GMRES + LU−SGS method leads to a significant increase in performance over the LU−SGS method, while maintaining memory requirements similar to its explicit counterpart. An overall speedup factor from one to more than two order of magnitude for all test cases in comparison with the explicit method is demonstrated.
Abstract
A fast, matrix-free implicit method has been developed to solve low Mach number flow problems on unstructured grids. The preconditioned compressible Euler and Navier-Stokes [...]
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Flow and dispersion around buildings: An application with FLEFLO
F. Camelli, R. Lohner

(2000). European Congress on Computational Methods in Applied Sciences and Engineering

Abstract
A series of simulations were performed in order to test the accuracy of FEFLO for problems of flow and dispersion around buildings. The major case was extracted from the Evaluation of Modelling Uncertainty (project EMU)[1]. The simulations were run in "black box" mode, i.e. no tuning of parameters was allowed. The results obtained were in very close agreement with the available wind-tunnel data for the case selected. The accuracy is comparable with other codes. The results show that an Euler run with proper profile yields a fairly accurate answer.
Abstract
A series of simulations were performed in order to test the accuracy of FEFLO for problems of flow and dispersion around buildings. The major case was extracted from the Evaluation [...]
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Measurement of stenosis from Magnetic resonance angiography using vessel skeletons
P. Yim, R. Mullick, R. Summers, H. Marcos, J. Cebral, R. Lohner, P. Choyke

(2000). Proceedings Volume 3978, Medical Imaging 2000: Physiology and Function from Multidimensional

Abstract
Measurement of stenosis due to atherosclerosis is essential for interventional planning. Currently, measurement of stenosis from magnetic resonance angiography (MRA) is made based on 2D maximum intensity projection (MIP) images. This methodology, however, is subjective and does not take full advantage of the 3D nature of MRA. To address these limitations we present a deformable model for reconstructing the vessel surface with particular application to the carotid artery. The deformable model is based on a cylindrical coordinate system of a curvilinear axes. In this coordinate system, the location of each point on the surface of the deformable model is described by its axial, circumferential and radial position. The points on the surface deform in the radial direction so as to minimize discontinuity in radial position between adjacent points while maximizing the proximity of the surface to local edges in the image. The algorithm has no bias towards either narrower or wider cross- sectional shapes and is thus appropriate for the measurement of stenosis. Axes of the vessels are indicated manually or determined by axes detection methods. Once completed, the surface reconstruction lends itself directly to 3D methods for measuring cross-sectional diameter and area.
Abstract
Measurement of stenosis due to atherosclerosis is essential for interventional planning. Currently, measurement of stenosis from magnetic resonance angiography (MRA) is made [...]
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Generation of non‐isotropic unstructured grids via directional enrichment
R. Lohner, J. Cebral

Int. J. Numer. Meth. Engng. (2000). Vol. 49 (1-2), pp. 219-232

Abstract
A procedure for the generation of highly stretched grids suitable for Reynolds‐averaged Navier–Stokes (RANS) calculations is presented. In a first stage, an isotropic (Euler) mesh is generated. In a second stage, this grid is successively enriched with points in order to achieve highly stretched elements. The element reconnection is carried out using a constrained Delaunay approach. Points are introduced from the regions of lowest stretching towards the regions of highest stretching. The procedure has the advantages of not requiring any type of surface recovery, not requiring extra passes or work to mesh concave ridges/corners, and guarantees a final mesh, an essential requirement for industrial environments. Given that point placement and element quality are highly dependent for the Delaunay procedure, special procedures were developed in order to obtain optimal point placement.
Abstract
A procedure for the generation of highly stretched grids suitable for Reynolds‐averaged Navier–Stokes (RANS) calculations is presented. In a first stage, an isotropic [...]
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CFD Applications in Support of the Space Shuttle Risk Assessment
J. Baum, E. Mestreau, H. Luo, D. Sharov, R. Lohner

(2000). 1st Modeling and Simulation Subcommittee; November 13, 2000 - November 17, 2000; Monterey, CA; United States

Abstract
The paper describes a numerical study of a potential accident scenario of the space shuttle, operating at the same flight conditions as flight 51L, the Challenger accident. The interest in performing this simulation is derived by evidence that indicates that the event itself did not exert large enough blast loading on the shuttle to break it apart. Rather, the quasi-steady aerodynamic loading on the damaged, unbalance vehicle caused the break-up. Despite the enormous explosive potential of the shuttle total fuel load (both liquid and solid), the post accident explosives working group estimated the maximum energy involvement to be equivalent to about five hundreds of pounds of TNT. This understanding motivated the simulation described here. To err on the conservative side, we modeled the event as an explosion, and used the maximum energy estimate. We modeled the transient detonation of a 500 lbs spherical charge of TNT, placed at the main engine, and the resulting blast wave propagation about the complete stack. Tracking of peak pressures and impulses at hundreds of locations on the vehicle surface indicate that the blast load was insufficient to break the vehicle, hence demonstrating likely crew survivability through such an event.
Abstract
The paper describes a numerical study of a potential accident scenario of the space shuttle, operating at the same flight conditions as flight 51L, the Challenger accident. [...]
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On the Computation of Compressible Turbulent Flows on Unstructured Grids
H. Luo, D. Sharov, J. Baum, R. Lohner

Int. J. Numer. Meth. Fluids (2001). Vol. 14 (4), pp. 253-270

Abstract
An accurate, fast, matrix-free implicit method has been developed to solve compressible turbulent How problems using the Spalart and Allmaras one equation turbulence model on unstructured meshes. The mean-flow and turbulence-model equations are decoupled in the time integration in order to facilitate the incorporation of different turbulence models and reduce memory requirements. Both mean flow and turbulent equations are integrated in time using a linearized implicit scheme. A recently developed, fast, matrix-free implicit method, GMRES+LU-SGS, is then applied to solve the resultant system of linear equations. The spatial discretization is carried out using a hybrid finite volume and finite element method, where the finite volume approximation based on a containment dual control volume rather than the more popular median-dual control volume is used to discretize the inviscid fluxes, and the finite element approximation is used to evaluate the viscous flux terms. The developed method is used to compute a variety of turbulent flow problems in both 2D and 3D. The results obtained are in good agreement with theoretical and experimental data and indicate that the present method provides an accurate, fast, and robust algorithm for computing compressible turbulent flows on unstructured meshes.
Abstract
An accurate, fast, matrix-free implicit method has been developed to solve compressible turbulent How problems using the Spalart and Allmaras one equation turbulence model [...]
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Practical CFD Applications to Design of a Wave Cancellation Multihull Ship
C. Yang, F. Noblesse, R. Lohner, D. Hendrix

(2001). Twenty-Third Symposium on Naval Hydrodynamics, pp. 206-222

Abstract
Four methods of analysis — a nonlinear method based on Euler's equations and three linear potential flow methods — are used to determine the optimal lo- cation of the outer hulls for a wave cancellation mul- tihull ship that consists of a main center hull and two outer hulls. The three potential flow methods corre- spond to a hierarchy of simple approximations based on the Fourier-Kochin representation of ship waves and the slender-ship approximation.
Abstract
Four methods of analysis — a nonlinear method based on Euler's equations and three linear potential flow methods — are used to determine the optimal lo- cation [...]
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Time-Accurate Implicit ALE Algorithm for Shared-Memory Parallel Computers
D. Sharov, H. Luo, J. Baum, R. Lohner

(2001). Computational Fluid Dynamics 2000. Springer, Berlin, Heidelberg

Abstract
An unstructured grid matrix-free GMRES+LU-SGS scheme is used to simulate unsteady CFD problems with moving bodies. The method is applied on sharedmemory, cache-based parallel machines. A special grid renumbering technique is used for the parallelization rather than the traditional method of partitioning the computational domain. Moving mesh with recurrent remeshing models the body motion.
Abstract
An unstructured grid matrix-free GMRES+LU-SGS scheme is used to simulate unsteady CFD problems with moving bodies. The method is applied on sharedmemory, cache-based parallel [...]
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A Coupled CFD/CSD Methodology for Simulating Structural Response to Airblast and Fragment
J. Baum, H. Luo, E. Mestreau, R. Lohner, D. Pelessone, C. Charman

(2001). Computational Fluid Dynamics 2000. Springer, Berlin, Heidelberg

Abstract
Several classes of important engineering problems require the concurrent application of CFD and CSD techniques. Currently, attempts to model these problems are solved either iteratively, requiring several cycles of CFD run followed by CSD run, or by assuming that the CFD and CSD solutions can be decoupled. The various efforts to develop a fluid/structure coupling can be classified according to the complexity level of the approximations used for each of the domains. These range from simple 6 DOF integration to finite elements with complex models for elasto-plastic materials with rupture laws and contact. Similarly, the fluid dynamics approximations range from the potential flow (irotational, inviscid, isentropic flows) to the full Navier-Stokes set of equations. The present research interests focus on non-linear applications, in particular, structures that experience severe deformations due to blast loads. Hence, the fluid applies either the Euler or Reynolds-Averaged Navier-Stokes equations, while elasto-plastic materials with rupture criteria are used for the structural modeling.
Abstract
Several classes of important engineering problems require the concurrent application of CFD and CSD techniques. Currently, attempts to model these problems are solved either [...]
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An accurate, fast, matrix-free implicit method for computing unsteady flows on unstructured grids
H. Luo, J. Baum, R. Lohner

Computers and Fluids (2001). Vol. 30 (2), pp. 137-159

Abstract
An accurate, fast, matrix-free implicit method has been developed to solve the three-dimensional compressible unsteady flows on unstructured grids. A nonlinear system of equations as a result of a fully implicit temporal discretization is solved at each time step using a pseudo-time marching approach. A newly developed fast, matrix-free implicit method is then used to obtain the steady-state solution to the pseudo-time system. The developed method is applied to compute a variety of unsteady flow problems involving moving boundaries. The numerical results obtained indicate that the use of the present implicit method leads to a significant increase in performance over its explicit counterpart, while maintaining a similar memory requirement.
Abstract
An accurate, fast, matrix-free implicit method has been developed to solve the three-dimensional compressible unsteady flows on unstructured grids. A nonlinear system of equations [...]
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New methods for computational fluid dynamics modeling of carotid artery from magnetic resonance angiography
J. Cebral, P. Yim, R. Lohner, O. Soto, H. Marcos, P. Choyke

(2001). Proceedings Volume 4321, Medical Imaging 2001: Physiology and Function from Multidimensional

Abstract
Computational fluid dynamics (CFD) models of the carotid artery are constructed from contrast-enhanced magnetic resonance angiography (MRA) using a deformable model and a surface-merging algorithm. Physiologic flow conditions are obtained from cine phase-contrast MRA at two slice locations below and above the carotid bifurcation. The methodology was tested on image data from a rigid flow-through phantom of a carotid artery with 65% degree stenosis. Predicted flow patterns are in good agreement with MR flow measurements at intermediate slice locations. Our results show that flow in a rigid flow-through phantom of the carotid bifurcation with stenosis can be simulated accurately with CFD. The methodology was then tested on flow and anatomical data from a normal human subject. The sum of the instantaneous flows measured at the internal and external carotids differs from that at the common carotid, indicating that wall compliance must be modeled. Coupled fluid-structure calculations were able to reproduce the significant dampening of the velocity waveform observed between different slices along the common carotid artery. Visualizations of the blood flow in a compliant model of the carotid bifurcation were produced. A comparison between compliant and rigid models shows significant differences in the time-dependent wall shear stress at selected locations. Our results confirm that image-based CFD techniques can be applied to the modeling of hemodynamics in compliant carotid arteries. These capabilities may eventually allow physicians to enhance current image-based diagnosis, and to predict and evaluate the outcome of interventional procedures non- invasively.
Abstract
Computational fluid dynamics (CFD) models of the carotid artery are constructed from contrast-enhanced magnetic resonance angiography (MRA) using a deformable model and a [...]
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Interpretation of arterial velocity waveforms
P. Yim, J. Cebral, R. Lohner, P. Choyke, H. Marcos, O. Soto

(2001). Proceedings Volume 4321, Medical Imaging 2001: Physiology and Function from Multidimensional

Abstract
Blood flow temporal waveforms change with position along an artery. The change in the flow waveforms can be accounted for by a transmission line model of flow. According to this model, pulse waves propagate at a finite velocity in both directions along the artery. In principle, given flow waveforms measured at three locations along an artery, the pulse-wave velocity, (c) can be determined from the wave equation (d2Q/dt2 equals c2d2Q/dz2, Q is flow, t is time, z is position). Given the vessel diameter, the vessel-wall compliance can be derived from pulse-wave velocity. However, direct solution of the wave equation for pulse-wave velocity is highly susceptible to flow-measurement error. Thus, we propose a new method for estimating pulse-wave velocity from arterial flow waveforms. In our method, ideal flow waveforms are reconstructed from three measured flow waveforms. The ideal waveforms are reconstructed by minimization of the total error between the ideal and measured waveforms subject to constraints of the wave equation. Ideal flow waveforms are reconstructed for a range of assumed pulse-wave velocities. The true pulse-wave velocity is considered to be that which produces the minimum total error. The method applied to blood flow measurements made with phase-contrast magnetic resonance imaging.
Abstract
Blood flow temporal waveforms change with position along an artery. The change in the flow waveforms can be accounted for by a transmission line model of flow. According to [...]
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Unstructured Navier–Stokes grid generation at corners and ridges
D. Sharov, H. Luo, J. Baum, R. Lohner

Int. J. Numer. Meth. Fluids (2003). Vol. 43 (6-7), pp. 717-728

Abstract
Problems related to automatic generation of highly stretched unstructured grids suitable for 3‐D Reynolds‐averaged Navier–Stokes computations are addressed. Special attention is given to treatment of such geometrical irregularities as convex and concave ridges as well as corners where the ridges meet. The existing unstructured grid generation approaches may fail or produce poor quality meshes in such geometrical regions. The proposed solution is based on special meshing of non‐slip body surfaces resulting in smooth and robust volume meshing and high overall quality of generated grids. Several examples demonstrate the efficiency of the method for complex 3‐D geometries.
Abstract
Problems related to automatic generation of highly stretched unstructured grids suitable for 3‐D Reynolds‐averaged Navier–Stokes computations are addressed. Special [...]
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CFD shape optimization using an incomplete-gradient adjoint formulation
O. Soto, R. Lohner

Int. J. Numer. Meth. Engng. (2001). Vol. 51 (6), pp. 735-753

Abstract
A design methodology based on the adjoint approach for flow problems governed by the incompressible Euler equations is presented. The main feature of the algorithm is that it avoids solving the adjoint equations, which saves an important amount of CPU time. Furthermore, the methodology is general in the sense it does not depend on the geometry representation. All the grid points on the surface to be optimized can be chosen as design parameters. In addition, the methodology can be applied to any type of mesh. The partial derivatives of the Row equations with respect to the design parameters are computed by finite differences. In this way, this computation is independent of the numerical scheme employed to obtain the Row solution. Once the design parameters have been updated, the new solid surface is obtained with a pseudo-shell approach in such a way that local singularities, which can degrade or inhibit the convergence to the optimal solution, are avoided. Some 2D and 3D numerical examples are shown to demonstrate the proposed methodology.
Abstract
A design methodology based on the adjoint approach for flow problems governed by the incompressible Euler equations is presented. The main feature of the algorithm is that [...]
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A parallel advancing front grid generation scheme
R. Lohner

Int. J. Numer. Meth. Engng. (2001). Vol. 51 (6), pp. 663-678

Abstract
A parallel advancing front scheme has been developed. The domain to be gridded is first subdivided spatially using a relatively coarse octree. Boxes are then identified and gridded in parallel. A scheme that resembles closely the advancing front technique on scalar machines is recovered by only considering the boxes of the active front that generate small elements. The procedure has been implemented on the SGI origin class of machines using the shared memory paradigm. Timings for a variety of cases show speedups similar to those obtained for flow codes. The procedure has been used to generate grids with tens of millions of elements.
Abstract
A parallel advancing front scheme has been developed. The domain to be gridded is first subdivided spatially using a relatively coarse octree. Boxes are then identified and [...]
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CLOUD TECHNOLOGY: A CATALYST FOR EFFECTIVE ENTREPRENEURSHIP EDUCATION IN NIGERIA