JOURNALS

Documents published in Scipedia

• A coupled Eulerian-Pfem model for the simulation of overtropping in rockfill dams

  A. Larese, E. Oñate, R. Rossi

  Monograph CIMNE (2012). M133

  
  

  Abstract

  Rockfill dams are nowadays often preferred over concrete dams because of their economic advantages, their flexible and thank to the great advance achieved in geosciences and geomechanics. Unfortunately their behavior in case of overtopping is still an open issue. In fact very little is known on this phenomenon that in most cases leads to the complete finite failure o the structure with catastrophic consequences in term of loss of lives and economic damage. The principal aim of the present work is the development of a computational method to simulate the overtopping and the beginning of failure of the downstream shoulder of a rockfill dam. The whole phenomenon is treated in a continuous framework. The fluid free surface problem outside and inside the rockfill slop e is treated using a unique Eulerian fixed mesh formulation. A level set technique is employed to track the evolution of the free surface. The traditional Navier-Stokes equations are modified in order to automatically detect the presence of the porous media. The non-linear seepage is evaluated using a quadratic form of the resistance law for which the Ergun's coefficients have been chosen.  

  Abstract
  Rockfill dams are nowadays often preferred over concrete dams because of their economic advantages, their flexible and thank to the great advance achieved in geosciences and [...]

  • 67
  •  read

• Coupled wave-structure analysis for naval and offshore applications

  J. García-Espinosa, B. Servan Camas, D. Di Capua, P. Ubach de Fuentes, E. Oñate

  V Computational Methods in Marine Engineering (Marine 2013) , Hamburg (Germany)

  
  

  Abstract

  Wave-structure interaction is a topic of great interest in naval and offshore engineering. This interest is growing in the last years due to the boost given by the development of the marine renewable energy field. In this context the development of an efficient time-domain coupled waves-structure solver is a main request from the industry. Up to date the numerical seakeeping simulation has been mostly carried out using the frequency domain. The reason might be that the computational cost of time domain simulations were too high and computational time was too large. Moreover assumptions like linear waves and the harmonic nature of water waves made the frequency domain to be the right choice. However nowadays computing capabilities make possible to carry out numerical simulations in the time domain in a reasonable time, with the advantage of making easier the introduction of non-linearities into the algorithm and therefore coupling with other phenomena. This presentation shows the work of the authors in developing a time-domain unstructured Finite Element Method (FEM) algorithm for analysis of coupled wave-structure interaction. For this purpose, a new diffraction-radiation solver using the FEM was developed. The solver has been implemented in GPU, using CUDA architecture. The speed-up obtained ranges from 5 to 10 times compare to the implementation in a standard CPU with a conjugate gradient and ILU preconditioner. The seakeeping analysis tool has been integrated within a coupled waves-structure analysis tool. The coupling algorithm is based on a partitioned iterative algorithm, using an interpolation library able to communicate pressure forces and displacements of the structure at memory level. Furthermore, an innovative wetting and drying scheme able to improve the evaluation of the water action on the structure. The accuracy of the new seakeeping formulation for analysis of waves and floating structures interaction has been verified in different validation cases and practical applications. 

  Abstract
  Wave-structure interaction is a topic of great interest in naval and offshore engineering. This interest is growing in the last years due to the boost given by the development [...]

  • 64
  •  read

• Evaluating performance of the air cushion and seals of a Surface-Effect Ship (SES)

  J. García-Espinosa, B. Servan Camas, D. Di Capua, P. Ubach de Fuentes, E. Oñate

  Presentations Repository of the International Centre for Numerical Methods in Engineering (CIMNE) (2013).

  
  

  Abstract

  This presentation shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a stream-line integration of the free surface. The presentation focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behavior of the seals in the interface between the air cushion, and the water. The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken’s method. Several validations against experimental results have been carried out to demonstrate the developed algorithm.

  Abstract
  This presentation shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid [...]

  • 88
  •  read

• A computational model for the evaluation of the spray generation of a Wave Adaptive Modular Vessel

  J. García-Espinosa, E. Oñate, B. Servan Camas, P. Nadukandi, P. Becker

  Presentations Repository of the International Centre for Numerical Methods in Engineering (CIMNE) (2016).

  
  

  Abstract

  A Wave Adaptive Modular Vessel (WAM-V®) is a new class of ship that uses inflatable flexible hulls to conform to the surface of the water. It is similar in design to a catamaran, in that it has a twin hull design and no keel. However, the superstructure is not rigidly attached to the hulls; it uses shock absorbers and ball joints to articulate the vessel, which allows WAM-V to conform to the surface of the water while mitigating the stresses transmitted to the structure. Moreover, the inflatable hulls help to absorb the high frequency wave-loads. These features allow WAM-V to travel efficiently with low wave resistance in rough seas, by surfing on top of the waves rather than cut through them. The objective of the WAM-V is to be a lightweight watercraft capable of moving fast and efficiently on the surface of the sea. WAM-Vs are designed to allow for a variety of applications for either manned or unmanned operations and can be built in different lengths to match specific services. This presentation shows part of the work done in the project ‘Advanced Numerical Simulation and Performance Evaluation of WAM-V ® in Spray Generating Conditions’ developed by the International Center for Numerical Methods in Engineering (CIMNE) under Navy Grant N62909-12-1-7101 issued by the Office of Naval Research Global. The scope of that project included the performance analysis of the WAM-V in waves, taking into account the flexibility of the ship hulls, using fluid-structure interaction computational models. However, the focus of this paper is one of the primary concerns of that project; the development of a computational model for simulation of the WAM-V under spray generating conditions. In this regards, the final goal was to develop and demonstrate a computational engineering solver that could be used to design strategies to reduce the spray generation of the vessel.

  Abstract
  A Wave Adaptive Modular Vessel (WAM-V®) is a new class of ship that uses inflatable flexible hulls to conform to the surface of the water. It is similar in design to a [...]

  • 47
  •  read

• Advances in the Development of the Discrete Element Method for Excavation Processes

  C. Labra, E. Oñate, J. Rojek

  Monograph CIMNE (2012). M132

  
  

  Abstract

  Modelling of granular materials, soils and rocks has been a challenging topic of investigation for decades. Classical continuum mechanics has been used to idealize soils and rocks, and numerical solution techniques such as finite element method (FEM) has been used to model these materials. Considering the idealization of the material, continuum mechanics allows the analysis of phenomena with discontinuous nature such as fracture in rock or soil via damage models. However, in more complex processes like rock milling or crushing, this kind of models are usually not suitable. Discrete models are more appropriate for problems with multiple discontinuities and particulate materials. The discrete element method (DEM) has been gaining popularity in analysis of granular materials, soils and rocks. Many aspects of this method still require more profound investigation. This work presents new developments of the discrete element method improving efficiency and accuracy of modelling of rock-like materials, especially in excavation processes. All the numerical algorithms has been implemented in an in-house software, which was then used to run numerical examples. The basic formulation of DEM with linear elastic-perfectly brittle contact model is presented. The main difference with other models found in the literature is the consideration of global stiffness and strength parameters that are constants in the whole model. The result of a simulations is strongly related with the configuration of the particle assembly used. Particle assemblies should be suficiently compact and ensure the isotropy to reproduce the physical properties of the modelled material. This work presents a novel technique for the generation of highly dense particle assemblies in arbitrary geometries, satisfying all the requirements for accurate discrete element simulations. One of the key issues in the use of the DEM is the estimation of the contact model parameters. A methodology is proposed for the estimation of the contact model parameters yielding required macroscopic properties of the material. The relationships between the contact model parameters and the mechanical properties of brittle materials, as well as the influence of the particles assembly configuration on the macroscopic properties, are analysed. A major dificulty in the application of the DEM to real engineering problems is the high computational cost in simulation involving a large number of particles. The most common way to solve this is the use of parallel computing techniques, where multiple processors are used. As an alternative, a coupling scheme between DEM and the finite element method (FEM) is proposed in the work. Within the hybrid DEM/FEM model, DEM is only used in the region of the domain where it provides an advantage over a continuum-based approach, as the FEM. The coupling is dynamically adapted, starting with the whole domain discretized with FEM. During the simulation, in the regions where a high stress level are found, a change of modelling method from continuum FEM to the discrete DEM is employed. Finally, all the developments are applied to the simulation of a real excavation process. An analysis of the rock cutting process with TBM disc cutters is performed, where DEM and the DEM/FEM coupling technique presents an important advantage over other simulation techniques.

  Abstract
  Modelling of granular materials, soils and rocks has been a challenging topic of investigation for decades. Classical continuum mechanics has been used to idealize soils and [...]

  • 238
  •  read

• Desarrollo de una Herramienta de Procesamiento de Imágenes Médicas en MATLAB y su Integración en Medical GiD

  G. Gavidia, M. Cerrolaza, E. Oñate, E. Soudah, J. Pérez

  (2009). Technical Report, IT595

  
  

  Abstract

  El rápido avance de las tecnologías de adquisición de imágenes médicas ha hecho necesario el desarrollo de diversas aplicaciones en el área de la biomedicina. Por un lado, el trabajo que los médicos desarrollan en cuanto al análisis de las imágenes, es arduo y sujeto a errores, por lo que se hace necesaria la implementación de algoritmos de procesamiento que automaticen esta tarea y sirvan de soporte a los profesionales de la salud para realizar un diagnóstico fiable. Por otro lado, los biomédicos dedicados al modelado y simulación del cuerpo humano y el diseño de prótesis e implantes para tratamiento médico, requieren de modelos geométricos que consideren la complejidad característica de las estructuras anatómicas del cuerpo humano y les permita realizar un modelado discreto más preciso. Es por esto, que la comunidad de biomédicos, particularmente el área de analistas de imágenes médicas, hoy en día, dedican sus esfuerzos a extraer con ayuda del ordenador, información clínica, cualitativa y cuantitativa de las estructuras del cuerpo humano: tejidos blandos, duros, fluidos y sus patologías a partir del procesamiento de imágenes médicas de diversas modalidades: Tomografía Computarizada, Resonancia Magnética, Medicina Nuclear, entre otras.

  Abstract
  El rápido avance de las tecnologías de adquisición de imágenes médicas ha hecho necesario el desarrollo de diversas aplicaciones en el área [...]

  • 7
  •  read

• CIMNE Verification of the validation analysis of Xfinas elements database

  E. Oñate, A. Larese

  (2009). Technical Report, IT570

  
  

  Abstract

  In order to validate the Xfinas code a very comprehensive series of test examples were solved by Prof Ki-Du Kim and his co-workers. A collection of the more representative benchmarks were chosen at CIMNE for testing the good behavior of every element implemented in the software. The aim of the validation work carried out at CIMNE has been to asses the accuracy of the Xfinas program. This was done studying the whole validation process carried out by Prof Ki-Du Kim’s team in detail. For this purpose we have chosen at CIMNE randomly the different benchmarks to be reproduced between those of the validation manual (VM from now on). In every example we checked the agreement of the results with the Xfinas validation data.

  Abstract
  In order to validate the Xfinas code a very comprehensive series of test examples were solved by Prof Ki-Du Kim and his co-workers. A collection of the more representative [...]

  • 18
  •  read

• BIMtable: your digital office at the building site

  J. Mora, G. Peffer, E. Oñate

  Presentations Repository of the International Centre for Numerical Methods in Engineering (CIMNE) (2017).

  
  

  Abstract

  The digitization process applied to the construction sector seems to be articulated through the "Building Information Modeling" (BIM), which, as is well known, includes not only the three-dimensional (3D) representation of the works, but its many other dimensions, such as temporal information, budget, sustainability, services, etc. The BIM, as a technology, process and ecosystem, is effectively offering solutions for the entire life cycle of a project, in its design, execution and operation phases, and for all the agents linked to it, that is, for all the professionals of the construction sector without exception. The BIMtable concept is born from considering that it is precisely the construction, the most complex environment - changing and severe - the most interesting scenario to incorporate the novelties offered by the BIM, as well as all the technologies that complement it, to achieve the digitalization of the construction in its broadest sense. It is at the work site where real-time monitoring of its progress can be made, using sensors, IoT, cameras or the information provided by the workers themselves. It is in the construction where the different professionals need to access the information of the project, as it has been developed and modeled, to follow and execute the instructions of the architect.

  Abstract
  The digitization process applied to the construction sector seems to be articulated through the "Building Information Modeling" (BIM), which, as is well known, includes [...]

  • 86
  •  read

• A coupled FEM-DEM procedure for predicting blasting operations in tunnels

  F. Zarate, J. Gonzalez, J. Miquel, R. Lohner, E. Oñate

  Underground Space (2018). Vol. 3 (3), pp. 310-316

  
  

  Abstract

  We present recent developments in the coupling of the finite element method (FEM) and the discrete element method (DEM) for analysis of rock blasting operations in tunnels. The coupled FEM-DEM technique has proven to be an efficient technique for predicting the multi-fracture of rock induced by the loads generated in blasting situations. The coupled FEM-DEM procedure is applied in the tunnel construction, as well as to gas pressure blasting pyrotechnics situations to break rock for excavation of the tunnel front. In the latter case the effect of gas explosion is modelled by solving with the FEM the equations of gas dynamics in the analysis domain. The effect of the gas forces in the underlying rock mass is modelled with an embedded fluid-structure interaction method. This allows us to accurately predicting the progressive multi-fracture of the rock accounting for the penetration of the gas in the fractured domain modelled with the FEM-DEM procedure. The efficiency of the coupled FEM-DEM technique is demonstrated in several examples of fracture tests and rock blasting problems related to tunnel engineering'''.''' The examples presented show that the combination of the DEM with simple 3-noded linear triangular elements correctly captures the onset of fractures and their evolution [1].

  Abstract
  We present recent developments in the coupling of the finite element method (FEM) and the discrete element method (DEM) for analysis of rock blasting operations in tunnels. [...]

  • 300
  • 5/5
  •  read

• Advances in the DEM and coupled DEM and FEM techniques in non linear solid mechanics

  E. Oñate, F. Zarate, M. Celigueta, J. Gonzalez, J. Miquel, J. Carbonell, F. Garcia, S. Latorre, M. Santasusana

  (2017). Research Report, Nº PI416

  
  

  Abstract

  In this chapter we present recent advances in the Discrete Element Method (DEM) and in the coupling of the DEM with the Finite Element Method (FEM) for solving a variety of problems in non linear solid mechanics involving damage, plasticity and multifracture situations.

  Abstract
  In this chapter we present recent advances in the Discrete Element Method (DEM) and in the coupling of the DEM with the Finite Element Method (FEM) for solving a variety of [...]

  • 474
  •  read