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• Contribution to the fluid-structure interaction analysis of ultra-lightweight structures using an embedded approach

  D. Baumgärtner, J. Wolf, R. Rossi, R. Wüchner, P. Dadvand

  Monograph CIMNE (2015). M152

  
  

  Abstract

  Designing large ultra-lightweight structures within a fluid flow, such as inflatable hangars in an atmospheric environment, requires an analysis of the naturally occurring fluid-structure interaction (FSI). To this end multidisciplinary simulation techniques may be used. The latter, though, have to be capable of dealing with complex shapes and large deformations as well as challenging phenomena like wrinkling or folding of the structure. To overcome such problems the method of embedded domains may be used. In this work we discuss a new solution procedure for FSI analyses based on the method of embedded domains. In doing so, we are in particular answering the questions: How to track the interface in the embedded approach, how does the subsequent solution procedure look like and how does both compare to the well-known Arbitrary Lagrangian-Eulerian (ALE) approach? In this context a level set technique as well as different mapping and mesh-updating strategies are developed and evaluated. Furthermore the solution procedure of a completely embedded FSI analysis is established and tested using different small- and large-scale examples. All results are finally compared to results from an ALE approach. It is shown that the embedded approach offers a powerful and robust alternative in terms of the FSI analysis of ultra-lightweight structures with complex shapes and large deformations. With regard to the solution accuracy, however, clear restrictions are elaborated.

  Abstract
  Designing large ultra-lightweight structures within a fluid flow, such as inflatable hangars in an atmospheric environment, requires an analysis of the naturally occurring [...]

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• Innovative numerical tools for the simulation of parachutes

  E. Ortega, R. Flores, E. Oñate, C. Sacco, E. González

  (2010). Research Report, Nº PI341

  
  

  Abstract

  The design and evaluation of parachute-payload systems is an important field of applications in which numerical analysis tools can make very important contributions. This work describes new numerical developments carried out at CIMNE in this field, which involve a coupled fluid-structural solver intended for the unsteady simulation of ram-air type parachutes and a set of complementary tools aimed at studying trajectory and control systems effects. For an efficient solution of the aerodynamic problem, an unsteady panel method has been chosen exploiting the fact that large areas of separated flow are not expected under nominal flight conditions of ram-air parachutes. Besides, a dynamic explicit solver based on a finite element technique is chosen for the structure. This approach yields a robust solution even when highly non-linear effects due to large displacements and material asymmetric behaviours are present. The numerical results show considerable accuracy and robustness. An added benefit of the proposed aerodynamic and structural techniques is that they can be easily vectored and thus suitable for use in parallel architectures. The main features of the developed computational tools are described in this work and several numerical examples are provided to illustrate the good performance and potential of the proposed techniques. Further improvements of the methodology being carried out and future lines of investigation are also presented.

  Abstract
  The design and evaluation of parachute-payload systems is an important field of applications in which numerical analysis tools can make very important contributions. This [...]

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• Possibilities of the particle finite element method in computational mechanics

  E. Oñate, S. Idelsohn, M. Celigueta, R. Rossi, S. Latorre

  (2010). Research Report, Nº PI345

  
  

  Abstract

  We present some developments in the formulation of the Particle Finite Element Method (PFEM) for analysis of complex coupled problems in fluid and solid mechanics accounting for fluid-structure interaction and coupled thermal effects. The PFEM uses an updated Lagrangian description to model the motion of nodes (particles) in both the fluid and the structure domains. Nodes are viewed as material points which can freely move and even separate from the main analysis domain representing, for instance, the effect of water drops. A mesh connects the nodes defining the discretized domain where the governing equations are solved as in the standard FEM. The necessary stabilization for dealing with the incompressibility of the fluid is introduced via the finite calculus (FIC) method. An incremental iterative scheme for the solution of the non linear transient coupled fluid-structure problem is described. Extensions of the PFEM to allow for frictional contact conditions at fluid-solid and solid-solid interfaces via mesh generation are described. A simple algorithm to treat erosion in the fluid bed is presented. Examples of application of the PFEM to solve a number of coupled problems such as the effect of large wave on structures, the large motions of floating and submerged bodies, bed erosion situations and melting and dripping of polymers under the effect of fire are given.

  Abstract
  We present some developments in the formulation of the Particle Finite Element Method (PFEM) for analysis of complex coupled problems in fluid and solid mechanics accounting [...]

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• Interface GiD-SAP2000-VRML. Aplicación práctica a la modelización virtual de edificios del patrimonio histórico

  F. Muñoz, J. Maristany, J. López-Rey

  (2010). Research Report, Nº PI344

  
  

  Abstract

  The numerical modeling of historic buildings is an essential tool for understanding the structural behavior, even more whit the aim is to assume an analysis for conservation and / or rehabilitation. At present time, most building’s numerical simulation software is divided into three parts: the preprocessor, which prepares all the necessary information (geometry, boundary conditions, loads, etc.), the Analysis, where all calculations take place (FEM) and the postprocessing where decisions are taking based on the analysis of the results obtained in the previous steps (Muñoz, Maristany 1999). At that last point is, where the user of the computer programs usually find limitations in the graphical interpretation of the results. Some numerical results with endless list of numbers are not the best way to address the problem and its graphical output is not yet fully developed. That is, graphic interface is still very basic, let alone a real-time dynamic visualization in 3D. It`s important to have both powerful hardware and software tools to visualize the obtained results. Currently, there are emerging many structural analysis programs that have highly advanced postprocessing, but they still display limitations in space, they operate only on 2 or 3 dimensions with space constraints. For this reason, this paper seeks to integrate different current computer programs with 3D graphical representation. Thus, the visualization of numerical results (tension, stress and strain values) can be much more interesting. This is to enable users to virtually navigate in real time, through any 3D structure and better understand their behavior. In short, this research aims to develop an interface between the computer programs of structural calculations and representation software with virtual 3D graphics (vrml- virtual reality modeling language), with practical application to historic buildings. As a closure for the paper we develop a practical example based on Mexico City’s Cathedral tabernacle.

  Abstract
  The numerical modeling of historic buildings is an essential tool for understanding the structural behavior, even more whit the aim is to assume an analysis for conservation [...]

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• Explicit dynamic analysis of thin membrane structures

  R. Flores, E. Ortega, E. Oñate

  (2011). Research Report, Nº PI351

  
  

  Abstract

  An explicit dynamic structural solver developed at CIMNE for the analysis of parachutes is presented. The canopy fabric has a negligible out-of-plane stiffness, therefore its numerical study presents important challenges. Both the large changes in geometry and the statically indeterminate character of the system are problematic from the numerical point of view. This report covers the reasons behind the particular choice of solution scheme as well as a detailed description of the underlying algorithm. Both the theoretical foundations of the method and details of implementation aiming at improving computational efficiency are given. Benchmark cases to assess the accuracy of the solution as well as examples of practical application showing the performance of the code are finally presented.

  Abstract
  An explicit dynamic structural solver developed at CIMNE for the analysis of parachutes is presented. The canopy fabric has a negligible out-of-plane stiffness, therefore [...]

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• Development of a 6-DoF simulator for analysis and evaluation of autonomous parafoil systems

  E. González, C. Sacco, E. Ortega, R. Flores

  (2011). Research Report, Nº PI356

  
  

  Abstract

  The role parachutes have in many civil, humanitarian and military applications call for new and improved computational tools aimed at tackling the current lack of software applications in the field. The present project, which is part of a research line being developed at CIMNE for these purposes, involves the development of numerical tools for the analysis and evaluation of autonomous parafoil systems. These tools, which are based on a 6-DOF dynamic parachute model and a GNC system implemented by means of PID algorithms, facilitate the user to test designs, develop and evaluate control strategies and analyze real-life drop scenarios. As an example of potential use, lateral and altitude control strategies were successfully developed and tested. Future implementations will include Monte Carlo simulations for statistical analysis of landing precision, parameter identification for flight-tests data reduction and an advanced GUI. The dynamic simulator presented in this work, together with the aerodynamic and structural tools developed by CIMNE, allow simulating the complete parachute-payload system, letting the designer to analyse design variations before building prototypes, the control system engineer to test different control strategies and the flight test engineer to predict the real performance of the system even before flying it once. In brief, involving simulation in the whole development process increases chances of success, shortening development time and costs.

  Abstract
  The role parachutes have in many civil, humanitarian and military applications call for new and improved computational tools aimed at tackling the current lack of software [...]

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• The Cycle of Ideas in research, development and technology transfer

  E. Oñate

  (2011). Research Report, Nº PI358

  
  

  Abstract

  When people talks about research, development and technology transfer (RTD in short) and commercial industrial activities, it is quite usual to mix up objectives, resources and responsibilities. There is a growing opinion, spread by some public administrators and the media, that research groups at universities and RTD centers must be "profitable". In few words, many persons would wish that research is funded with competitive funds or even loans (either public or private) and that the outcomes of the research get into the market rapidly, so that the profits from marketing the corresponding products will allow research groups to be financially self-sustaining.

  Abstract
  When people talks about research, development and technology transfer (RTD in short) and commercial industrial activities, it is quite usual to mix up objectives, resources [...]

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• Advances on Finite Element Methods and Particle-based Methods for Metal Forming Processes

  E. Oñate

  (2011). Research Report, Nº PI360

  
  

  Abstract

  The paper presents an overview of the advances in recent years on the finite element method (FEM) and on particle-based methods for the simulation of industrial metal forming processes. More specifically, we present the evolution of the FEM in the field from the early plastic/viscoplastic flow approaches to the new stabilized FEM for analysis of multiphysics bulk forming processes. Also the paper describes the state of the art in the new rotation-free shell elements for simulation of sheet stamping processes. Finally, we present the so-called Particle Finite Element Method (PFEM), as a component of a family of new computational techniques integrating particle-based methods and mesh-based procedures. The PFEM is particularly suited for large deformation problems in solids and fluids involving nonlinear mechanical and geometrical effects, fluid-structure interactions and frictional contact situations. Applications of the FEM and the PFEM to several metal and material forming processes are presented.

  Abstract
  The paper presents an overview of the advances in recent years on the finite element method (FEM) and on particle-based methods for the simulation of industrial metal forming [...]

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• Análisis de flujos en lámina libre y su interacción con sólidos y estructuras por el método de partículas y elementos finitos (PFEM)

  E. Oñate, B. Suárez, F. Salazar, R. Morán, M. Celigueta, S. Latorre

  (2011). Research Report, Nº PI365

  
  

  Abstract

  Se describen los conceptos básicos del método de partículas y elementos finitos (PFEM) para análisis de flujos de fluidos en lámina libre y su interacción con objetos sólidos y estructuras flotantes o sumergidas. Se presentan diversas aplicaciones del PFEM en los ámbitos de la ingeniería de puertos e hidráulica y al estudio de la caída de una avalancha sobre un embalse.

  Abstract
  Se describen los conceptos básicos del método de partículas y elementos finitos (PFEM) para análisis de flujos de fluidos en lámina libre [...]

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• Modelització del deflectòmetre d’impacte amb el mètode dels elements finits i les partícules

  M. Font, E. Oñate, J. Carbonell

  (2011). Research Report, Nº PI366

  
  

  Abstract

  El deflectòmetre d’impacte segurament és l’aparell més utilitzat per realitzar assaigs no destructius dels ferms. Els enginyers utilitzen el deflectòmetre d’impacte per estimar els mòduls elàstics de les diferents capes que conformen el ferm assumint una aproximació quasi estàtica del fenomen. Amb la utilització del Mètode dels Elements Finits i les Partícules (PFEM), per una banda es pot simular l’impacte que provoca el deflectòmetre d’impacte sobre el ferm, i de l’altra validar el PFEM com a model axisimètric de resposta dinàmica d’un ferm. La validació consisteix a comparar la concavitat de deflexions mesurada pel deflectòmetre d’impacte amb la concavitat de deflexions calculada amb el PFEM utilitzant els mòduls elàstics que proporciona el càlcul invers. Els capítols 2 i 3 inclouen el marc teòric en el qual es desenvolupa el treball. El capítol 2 inclou una introducció als ferms, presenta el concepte de deflexió, fa un repàs dels equips d’avaluació no destructiva i presenta un resum dels diferents mètodes existents per al càlcul de paviments flexibles. El capítol 3 és una introducció al Mètode dels Elements Finits i les Partícules. El capítol 4 presenta els desenvolupaments dels objectius plantejats. Per últim, es presenten unes consideracions finals, que inclouen les conclusions, possibles millores del programa d’ordinador emprat i propostes de futures línies d’investigació. Els annexes inclouen els resultats de tots els casos calculats amb les taules i les gràfiques corresponents.

  Abstract
  El deflectòmetre d’impacte segurament és l’aparell més utilitzat per realitzar assaigs no destructius dels ferms. Els enginyers utilitzen [...]

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