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1 to 50 of 1485 results
  • A two-step monolithic method for efficient simulation of incompressible flows

     Ryzhakov, Pavel; Cotela Dalmau, Jordi; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio
    International journal for numerical methods in fluids
    Date of publication: 2014-04
    Journal article

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    We propose a simple technique for improving computational the eciency of monolithic velocity-pressure solvers for incompressible ow problems. The idea consists in solving the discrete non-linear system of governing equations in two steps: introducing \articial" compressibility rst and afterwards correcting the solution by solving the original incompressible system. The speed-up is obtained due to a better conditioning of the modied discrete system solved at the prediction step. The formulation can be easily implemented into existing monolithic codes requiring minor modication only. The paper concludes with two examples validating the formulation and facilitating the estimation of the obtained speed-up. For the tests chosen an average speed-up is appx. double, suggesting that the method is a feasible approach for incompressible flows' simulation.

    We propose a simple technique for improving computational the e ciency of monolithic velocity-pressure solvers for incompressible ow problems. The idea consists in solving the discrete non-linear system of governing equations in two steps: introducing \arti cial

  • Delamination in laminated plates using the 4-noded quadrilateral QLRZ plate element based on the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Composite structures
    Date of publication: 2014-02
    Journal article

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    A numerical method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated plate/shell structures is presented. The originality of this method is the use of 4-noded quadrilateral plate finite elements whit only seven variables per node to discretize the plate/shell geometry. The ability to capture the relative displacement between consecutive layers in fracture mode II and III is the more important advantage of this element, denoted QLRZ. A continuum isotropic damage model is used to model the mechanical behavior of the plies. The material non-lineal problem is solved with the modified Newton¿Raphson method. The RZT plate theory, the QLRZ finite element and the isotropic damage model are described in this work. Also, the implicit integration algorithm is presented. The performance of the numerical model is analyzed by studying the delamination in a rectangular plate for two different laminates, using the 3D analysis as the reference solution.

  • Comparative accuracy and performance assessment of the finite point method in compressible flow problems

     Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Flores Le Roux, Roberto Maurice
    Computers and fluids
    Date of publication: 2014-01-20
    Journal article

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    A comparative assessment of the Finite Point Method (FPM) is presented. Using a wing-fuselage configuration under transonic inviscid flow conditions as reference test case, the performance of the FPM flow solver is compared with an equivalent edge-based Finite Element (FEM) implementation. Efficiency issues have discouraged practical application of meshless methods in the past. Thus, a simplification of the basic FPM technique is proposed in order to reduce the performance gap with respect to classical grid-based algorithms. A comparative evaluation of the accuracy, computational cost and parallel performance of the meshless implementation is carried out with the objective to assess the level of maturity of the technique and identify improvements still required to tackle practical applications. The results obtained show accuracy and performance of the core algorithm comparable to a conventional FEM implementation, thus removing a major obstacle for further developments of the FPM.

  • Application of the finite point method to high- Reynolds number compressible flow problems

     Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Flores Le Roux, Roberto Maurice
    International journal for numerical methods in fluids
    Date of publication: 2014-04-10
    Journal article

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    In this work, the finite point method is applied to the solution of high-Reynolds compressible viscous flows. The aim is to explore this important field of applications focusing on two main aspects: the easiness and automation of the meshless discretization of viscous layers and the construction of a robust numerical approximation in the highly stretched clouds of points resulting in such domain areas. The flow solution scheme adopts an upwind-biased scheme to solve the averaged Navier-Stokes equations in conjunction with an algebraic turbulence model. The numerical applications presented involve different attached boundary layer flows and are intended to show the performance of the numerical technique. The results obtained are satisfactory and indicative of the possibilities to extend the present meshless technique to more complex flow problems. Copyright (c) 2014 John Wiley & Sons, Ltd.

    In this work, the finite point method is applied to the solution of high-Reynolds compressible viscous flows. The aim is to explore this important field of applications focusing on two main aspects: the easiness and automation of the meshless discretization of viscous layers and the construction of a robust numerical approximation in the highly stretched clouds of points resulting in such domain areas. The flow solution scheme adopts an upwind-biased scheme to solve the averaged Navier-Stokes equations in conjunction with an algebraic turbulence model. The numerical applications presented involve different attached boundary layer flows and are intended to show the performance of the numerical technique. The results obtained are satisfactory and indicative of the possibilities to extend the present meshless technique to more complex flow problems. Copyright (c) 2014 John Wiley & Sons, Ltd.

  • A particle finite element method (PFEM) for coupled thermal analysis of quasi and fully incompressible flows and fluid-structure interaction problems

     Oñate Ibáñez de Navarra, Eugenio; Franci, Alessandro; Carbonell Puigbo, Josep Maria
    Date of publication: 2014
    Book chapter

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    This book presents and discusses mathematical models, numerical methods and computational techniques used for solving coupled problems in science and engineering. It takes a step forward in the formulation and solution of real-life problems with a multidisciplinary vision, accounting for all of the complex couplings involved in the physical description. Simulation of multifaceted physics problems is a common task in applied research and industry. Often a suitable solver is built by connecting together several single-aspect solvers into a network. In this book, research in various fields was selected for consideration: adaptive methodology for multi-physics solvers, multi-physics phenomena and coupled-field solutions, leading to computationally intensive structural analysis. The strategies which are used to keep these problems computationally affordable are of special interest, and make this an essential book.

    This book presents and discusses mathematical models, numerical methods and computational techniques used for solving coupled problems in science and engineering. It takes a step forward in the formulation and solution of real-life problems with a multidisciplinary vision, accounting for all of the complex couplings involved in the physical description. Simulation of multifaceted physics problems is a common task in applied research and industry. Often a suitable solver is built by connecting together several single-aspect solvers into a network. In this book, research in various fields was selected for consideration: adaptive methodology for multi-physics solvers, multi-physics phenomena and coupled-field solutions, leading to computationally intensive structural analysis. The strategies which are used to keep these problems computationally affordable are of special interest, and make this an essential book.

  • Lagrangian formulation for finite element analysis of quasi-incompressible fluids with reduced mass losses

     Oñate Ibáñez de Navarra, Eugenio; Franci, Alessandro; Carbonell Puigbo, Josep Maria
    International journal for numerical methods in fluids
    Date of publication: 2014-04
    Journal article

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    We present a Lagrangian formulation for finite element analysis of quasi-incompressible fluids that has excellent mass preservation features. The success of the formulation lays on a new residual-based stabilized expression of the mass balance equation obtained using the finite calculus method. The governing equations are discretized with the FEM using simplicial elements with equal linear interpolation for the velocities and the pressure. The merits of the formulation in terms of reduced mass loss and overall accuracy are verified in the solution of 2D and 3D quasi-incompressible free-surface flow problems using the particle FEM (). Examples include the sloshing of water in a tank, the collapse of one and two water columns in rectangular and prismatic tanks, and the falling of a water sphere into a cylindrical tank containing water. Copyright (c) 2014 John Wiley & Sons, Ltd.

  • A stabilized finite element formulation for high-speed inviscid compressible flows using finite calculus

     Kouhi, Mohammad; Oñate Ibáñez de Navarra, Eugenio
    International journal for numerical methods in fluids
    Date of publication: 2014-04
    Journal article

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    This paper aims at the development of a new stabilization formulation based on the finite calculus (FIC) scheme for solving the Euler equations using the Galerkin FEM on unstructured triangular grids. The FIC method is based on expressing the balance of fluxes in a space-time domain of finite size. It is used to prevent the creation of instabilities typically present in numerical solutions due to the high convective terms and sharp gradients. Two stabilization terms, respectively called streamline term and transverse term, are added via the FIC formulation to the original conservative equations in the space-time domain. An explicit fourth-order Runge-Kutta scheme is implemented to advance the solution in time. The presented numerical test examples for inviscid flows prove the ability of the proposed stabilization technique for providing appropriate solutions especially near shock waves. Although the derived methodology delivers precise results with a nearly coarse mesh, a mesh refinement technique is coupled to the solution process for obtaining a suitable mesh particularly in the high-gradient zones. Copyright (c) 2014 John Wiley & Sons, Ltd.

  • Analysis of segmentally constructed prestressed concrete bridges using hexahedral elements with realistic tendon profiles

     Norachan, Pramin; Kim, Ki-Du; Oñate Ibáñez de Navarra, Eugenio
    Journal of structural engineering (New York, N.Y.)
    Date of publication: 2014-06
    Journal article

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    The paper presents a systematically numerical procedure based on the finite-element method for three-dimensional analysis of segmentally constructed prestressed concrete bridges using hexahedral elements including realistic tendon profiles. The enhanced assumed strain (EAS) is used in the formulation of the hexahedral element in order to improve the element performances. Both the geometric nonlinearity and time-dependent effects due to creep, shrinkage, and aging of the concrete and relaxation of the prestress are taken into account, while variations of the structural configuration due to changes of the structural geometry and boundary conditions during the construction process are also incorporated. To include realistic tendon profiles, the idealized prestressing tendon is represented by a system of piecewise linear prestressing segments. Several numerical examples in a wide range of prestressed concrete structures are presented to demonstrate the validity and efficiency of the proposed procedure. Finally, application to the erection of a segmentally erected prestressed concrete bridge is discussed at the end of the paper.

  • A shallow water model by finite point method

     Bouchart, Chinapat; Kanok-Nukulchai, Worsak; Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio
    International journal of computational methods
    Date of publication: 2014-02-01
    Journal article

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    In this paper, "finite point method" (FPM) is presented for modeling 2D shallow water flow problem. The method is based on the use of a weighted least-square approximation procedure, incorporating QR factorization and an iterative adjustment of local approximation parameters. The stabilization of the convective term in this present work is derived from the approximate Riemann solver proposed by Roe. The present method is shown to produce competitive accuracy in the comparisons with the analytical solutions and the well-known Galerkin characteristic-based split (CBS) algorithm.

  • P1/PO+ elements for incompressible flows with discontinuous material properties

     Oñate Ibáñez de Navarra, Eugenio; Nadukandi, Prashanth; Idelsohn Barg, Sergio Rodolfo
    Computer methods in applied mechanics and engineering
    Date of publication: 2014-04
    Journal article

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    We present a 3-noded triangle and a 4-noded tetrahedra with a continuous linear velocity and a discontinuous linear pressure field formed by the sum of an unknown constant pressure field and a prescribed linear field that satisfies the steady state momentum equations for a constant body force. The elements are termed P1/P0+ as the "effective" pressure field is linear, although the unknown pressure field is piecewise constant within each element. The elements have an excellent behavior for incompressible viscous flow problems with discontinuous material properties formulated in either Eulerian or Lagrangian descriptions. The necessary numerical stabilization for dealing with the inf-sup condition imposed by the incompressibility constraint and high convective effects (in Eulerian flows) is introduced via the Finite Calculus (FIC) approach. For the sake of clarity, the element derivation is presented first for the simpler Stokes equations written in the standard Eulerian frame. The extension of the formulation to the Navier-Stokes equations written in the Eulerian and Lagrangian frameworks is straightforward and is presented in the second part of the paper.; The efficiency and accuracy of the new P1/P0+ triangle is verified by solving a set of incompressible multifluid flow problems using a Lagrangian approach and a classical Eulerian description. The excellent performance of the new triangular element in terms of mass conservation and general accuracy for analysis of fluids with discontinuous material properties is highlighted. (C) 2014 Published by Elsevier B.V.

  • Development and applications of the Finite Point Method to compressible aerodynamics problems

     Ortega, Enrique
    Defense's date: 2014-05-12
    Universitat Politècnica de Catalunya
    Theses

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    En este trabajo se aborda el desarrollo del Método de Puntos Finitos (MPF) y su aplicación a problemas de aerodinámica de flujos compresibles. El objetivo principal es investigar el potencial de la técnica sin malla para la solución de problemas prácticos, lo cual constituye una de las limitaciones más importantes de los métodos sin malla.En primer lugar se estudia la aproximación espacial en el MPF, haciendo hincapié en aquéllos aspectos que pueden ser mejorados para incrementar la robustez y exactitud de la metodología. Se determinan rangos adecuados para el ajuste de los parámetros de la aproximación y su comportamiento en situaciones prácticas. Se propone además un procedimiento de ajuste automático de estos parámetros a fin de simplificar la aplicación del método y reducir la dependencia de factores como el tipo de problema y la intervención del usuario, sin afectar la flexibilidad de la técnica sin malla.A continuación se aborda el esquema de solución de las ecuaciones del flujo. La discretización de las mismas se lleva a cabo siguiendo métodos estándar, pero aprovechando las características de la técnica sin malla. Con el objetivo de abordar problemas prácticos, se pone énfasis en la robustez y eficiencia de la implementación numérica (se propone además una simplificación del procedimiento de solución). El comportamiento del esquema se estudia en detalle para evaluar su potencial y se analiza su exactitud, coste computacional y escalabilidad, todo ello en comparación con un método convencional basado en Elementos Finitos.Finalmente se presentan distintas aplicaciones y extensiones de la metodología desarrollada. Los ejemplos numéricos pretenden demostrar las capacidades del método y también aprovechar las ventajas de la metodología sin malla en áreas en que la misma puede ser de especial interés. Los problemas tratados incluyen, entre otras características, el refinamiento automático de la discretización, la presencia de fronteras móviles e interacción fluido-estructura, como así también una aplicación preliminar a flujos compresibles de alto número de Reynolds. Los resultados obtenidos muestran una exactitud satisfactoria. Además, en comparación con una técnica similar basada en Elementos Finitos, demuestran ser competitivos en términos del coste computacional. Esto indica que las ventajas de la metodología sin malla pueden ser explotadas con eficiencia, lo cual constituye un buen punto de partida para el desarrollo de ulteriores aplicaciones.

  • Desarrollo de código de elementos finitos para el estudio de piezas laminares bajo cargas dinámicas

     Oñate Ibáñez de Navarra, Eugenio
    Participation in a competitive project

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  • T-MAPPP - Training in Multiscale Analysis of multi-Phase Particulate Processes

     Larese, Antonia; Oñate Ibáñez de Navarra, Eugenio
    Participation in a competitive project

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  • Visualization For Extremely Large-Scale Scientific Computing (VELaSSCo)

     Oñate Ibáñez de Navarra, Eugenio; Mora Serrano, Francisco Javier
    Participation in a competitive project

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  • Desarrollo de un método numérico para análisis de fluidos con partículas y su interacción con estructuras

     Oñate Ibáñez de Navarra, Eugenio
    Participation in a competitive project

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  • Computational Particle Mechanics

     Oñate Ibáñez de Navarra, Eugenio
    Collaboration in journals

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  • Robust volume mesh generation for non-watertight geometries

     Coll Sans, Abel
    Defense's date: 2014-07-01
    Universitat Politècnica de Catalunya
    Theses

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    En l'actualitat gran part del temps emprat per córrer una simulació numèrica està dedicat al preprocés, especialment a les operacions de neteja de geometria i generació de malla. A més, aquestes operacions no són fàcils d'automatitzar degut a la seva forta dependència del model geomètric i sovint necessiten d'interacció humana. Moltes d'aquestes operacions són necessàries per aconseguir una definició topològicament hermètica de la geometria. Inclús amb una geometria neta, els mètodes clàssics de mallat (com els basats en Delaunay o avançament frontal) presenten punts febles crítics com la necessitat d'una certa qualitat de les malles de contorn o una transició de mides relativament suau. Aquests aspectes disminueixen la seva robustesa i impliquen un esforç extra a l'hora d'obtenir la malla final. Els mètodes de mallat basats en estructures 'octree' relaxen alguns d'aquests requeriments.En aquest treball es presenta un mallador basat en octree per tetraedres no estructurats. Un dels aspectes claus d'aquest mallador és que garanteix la generació de malla evitant moltes de les operacions de neteja de geometria. Es basa en els següents passos: encaixar un octree al model, refinar-lo seguint certs criteris, aplicar un patró de tetraedres a les cel·les de l'octree i adaptar-los a les zones properes als contorns a fi i efecte de representar acuradament la forma del domini. Un aspecte important i innovador de l'algorisme proposat és que manté la topologia del model a la malla final i preserva les seves característiques geomètriques.El mètode presentat utilitza un algorisme basat en la tècnica 'Ray Casting' per la identificació de les parts interiors i exteriors dels volums del model. Aquesta tècnica permet la generació de malla de volums inclús amb contorns que no tanquen hermèticament, i també obre l'ús del mallador a mètodes 'immersed' aplicant només petites modificacions a l'algorisme. Els principals avantatges del mallador presentat són: robustesa, no necessitat de definicions hermètiques dels contorns, independent de la qualitat de la malla de contorn, preservació de característiques geomètriques (cantonades i arestes abruptes), topologia original de la geometria garantida, representació precisa dels contorns, vàlid per mètodes 'immersed' i ràpid rendiment. L'ús del mallador estalvia molt de temps en la part del preprocés de la simulació numèrica gràcies a la seva robustesa que permet obviar la majoria d'operacions de neteja de geometria.S'ha dut a terme una implementació paral·lela amb memòria compartida de l'algorisme. L'efectivitat de l'algorisme i la seva implementació ha estat verificada mitjançant exemples de validació.

  • A meshless finite point method for the three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity

     Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Flores Le Roux, Roberto Maurice
    International journal for numerical methods in fluids
    Date of publication: 2013-10-10
    Journal article

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    A finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian¿Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid¿structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided.

  • A compressible lagrangian framework for modeling the fluid-structure interaction in the underwater implosion of an aluminum cylinder

     Kamran, Kazem; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo
    Mathematical models and methods in applied sciences
    Date of publication: 2013-02
    Journal article

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  • Robust active shock control bump design optimisation using hybrid parallel MOGA

     Lee, Dong Seop; Bugeda Castelltort, Gabriel; Periaux, Jacques; Oñate Ibáñez de Navarra, Eugenio
    Computers and fluids
    Date of publication: 2013
    Journal article

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  • Analysis of the discharge capacity of radial gated-spillways using CFD and ANN: Oliana Dam case study

     Salazar González, Fernando; Morán Moya, Rafael; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio
    Journal of hydraulic research
    Date of publication: 2013-03
    Journal article

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    The paper focuses on the analysis of radial-gated spillways, which is carried out by the solution of a numerical model based on the finite element method (FEM). The Oliana Dam is considered as a case study and the discharge capacity is predicted both by the application of a level-set-based free-surface solver and by the use of traditional empirical formulations. The results of the analysis are then used for training an artificial neural network to allow real-time predictions of the discharge in any situation of energy head and gate opening within the operation range of the reservoir. The comparison of the results obtained with the different methods shows that numerical models such as the FEM can be useful as a predictive tool for the analysis of the hydraulic performance of radial-gated spillways.

  • Multi-objective aerodynamic shape optimization using MOGA coupled to advanced adaptive mesh refinement

     Kouhi, Mohamed; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oñate Ibáñez de Navarra, Eugenio
    Computers and fluids
    Date of publication: 2013-12-15
    Journal article

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    This paper demonstrates the big influence of the control of the mesh quality in the final solution of aerodynamic shape optimization problems. It aims to study the trade-off between the mesh refinement during the optimization process and the improvement of the optimized solution. This subject is investigated in the transonic airfoil design optimization using an Adaptive Mesh Refinement (AMR) technique coupled to Multi-Objective Genetic Algorithm (MOGA) and an Euler aerodynamic analysis tool. The methodology is implemented to solve three practical design problems; the first test case considers a reconstruction design optimization that minimizes the pressure error between a predefined pressure curve and candidate pressure distribution. The second test considers the total drag minimization by designing airfoil shape operating at transonic speeds. For the final test case, a multi-objective design optimization is conducted to maximize both the lift to drag ratio (L/D) and lift coefficient (Cl). The solutions obtained with and without adaptive mesh refinement are compared in terms of solution improvement and computational cost. Numerical results clearly show that the use of adaptive mesh refinement can improve the solution accuracy while reducing significant computational cost in both single- and multi-objective design optimizations.

  • A contact algorithm for shell problems via Delaunay-based meshing of the contact domain

     Kamran, Kazem; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio
    Computational Mechanics
    Date of publication: 2013-07
    Journal article

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    The simulation of the contact within shells, with all of its different facets, represents still an open challenge in Computational Mechanics. Despite the effort spent in the development of techniques for the simulation of general contact problems, an all-seasons algorithm applicable to complex shell contact problems is yet to be developed. This work focuses on the solution of the contact between thin shells by using a technique derived from the particle finite element method together with a rotation-free shell triangle. The key concept is to define a discretization of the contact domain (CD) by constructing a finite element mesh of four-noded tetrahedra that describes the potential contact volume. The problem is completed by using an assumed-strain approach to define an elastic contact strain over the CD.

  • An efficient edge-based level set finite element method for free surface flow problems

     Rossi, Riccardo; Larese, Antonia; Dadvand, Pooyan; Oñate Ibáñez de Navarra, Eugenio
    International journal for numerical methods in fluids
    Date of publication: 2013-02
    Journal article

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    We present an efficient technique for the solution of free surface flow problems using level set and a parallel edge-based finite elementmethod. An unstructured semi-explicit solution scheme is proposed. A custom data structure, obtained by blending node-based and edge-based approaches is presented so to allow a good parallel performance. In addition to standard velocity extrapolation (for the convection of the level set function), an explicit extrapolation of the pressure field is performed in order to impose both the pressure boundary condition and the volume conservation. The latter is also improved with a modification of the divergence free constrain. The method is shown to allow an efficient solution of both simple benchmark cases and complex industrial examples.

    We present an efficient technique for the solution of free surface flow problems using level set and a parallel edge-based finite elementmethod. An unstructured semi-explicit solution scheme is proposed. A custom data structure, obtained by blending node-based and edge-based approaches is presented so to allow a good parallel performance. In addition to standard velocity extrapolation (for the convection of the level set function), an explicit extrapolation of the pressure field is performed in order to impose both the pressure boundary condition and the volume conservation. The latter is also improved with a modification of the divergence free constrain. The method is shown to allow an efficient solution of both simple benchmark cases and complex industrial examples.

  • A compressible Lagrangian framework for the simulation of the underwater implosion of large air bubbles

     Kamran, Kazem; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo
    Computer methods in applied mechanics and engineering
    Date of publication: 2013-03
    Journal article

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  • Access to the full text
    Migration of a generic multi-physics framework to HPC environments  Open access

     Dadvand, Pooyan; Rossi, Riccardo; Gil Gómez, Maria Luisa; Martorell Bofill, Xavier; Cotela Dalmau, Jordi; Juanpere Cañameras, Edgar; Idelsohn Barg, Sergio Rodolfo; Oñate Ibáñez de Navarra, Eugenio
    Computers and fluids
    Date of publication: 2013-07-10
    Journal article

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    Creating a highly parallelizable code is a challenge specially for Distributed Memory Machines (DMMs). Moreover, algorithms and data structures suitable for these platforms can be very different from the ones used in serial code. For this reason, many programmers in the field prefer to start their own code from scratch. However, for an already existing framework supported by a long-time expertise the idea of transformation becomes attractive in order to reuse the effort done during years of development. In this presentation we explain how a relatively complex framework but with modular structure can be prepared for high performance computing with minimum modification. Kratos Multi-Physics [1] is an open source generic multi-disciplinary platform for solution of coupled problems consist of fluid, structure, thermal and electromagnetic fields. The parallelization of this framework is performed with objective of enforcing the less possible changes to its different solver modules and encapsulate the changes as much as possible in its common kernel. This objective is achieved thanks to the Kratos design and also innovative way of dealing with data transfers for a multi-disciplinary code. This work is completed by the migration of the framework from the 86× architecture to the Marenostrum Supercomputing platform. The migration has been verified by a set of benchmarks which show high scalability, from which we present the Telescope problem in this paper.

    Creating a highly parallelizable code is a challenge specially for distributed memory machines (DMMs). Moreover, algorithms and data structures suitable for these platforms can be very different from the ones used in serial code. For this reason, many programmers in the field prefer to start their own code from scratch. However, for an already existing framework supported by a long-time expertise the idea of transformation becomes attractive in order to reuse the effort done during years of development. In this presentation we explain how a relatively complex framework but with modular structure can be prepared for high performance computing with minimum modification. Kratos Multi-Physics [1] is an open source generic multi-disciplinary platform for solution of coupled problems consist of fluid, structure, thermal and electromagnetic fields. The parallelization of this framework is performed with objective of enforcing the less possible changes to its different solver modules and encapsulate the changes as much as possible in its common kernel. This objective is achieved thanks to the Kratos design and also innovative way of dealing with data transfers for a multi-disciplinary code. This work is completed by the migration of the framework from the x86 architecture to the Marenostrum Supercomputing platform. The migration has been verified by a set of benchmarks which show high scalability, from which we present the Telescope problem in this paper.

  • A Contribution to the Finite Element Analysis of High-Speed Compressible Flows and Aerodynamics Shape Optimization  Open access

     Kouhi Esfahani, Mohammad
    Defense's date: 2013-09-30
    Universitat Politècnica de Catalunya
    Theses

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    El presente trabajo pretende contribuir a dos de los campos de investigación más interesantes en la aerodinámica, el análisis numérico de flujos compresibles a alta velocidad (Parte I) y la optimización de la forma aerodinámica (Parte II).La primera parte de este estudio se centra en la solución numérica de las ecuaciones de Navier-Stokes, que modelan el comportamiento de flujos compresibles a alta velocidad. La discretización espacial se lleva a cabo mediante el método de elementos finitos (FEM) y se pone especial énfasis en el desarrollo de una nueva formulación estabilizada basada en la técnica de cálculo de Incremento finitos (FIC). En este última, los términos de estabilización convectiva se obtienen de manera natural de las ecuaciones de gobierno a través de postulados de conservación y equilibrio de flujos en un dominio espacio-tiempo de tamaño finito. Ello lleva a la obtención de dos términos de estabilización que funcionan de manera complementaria. Uno actúa en dirección de las líneas de corriente proporcionando la estabilización necesaria para contrarestrar las inestabilidades propias de la forma discreta de Galerkin y el otro término, de tipo shock capturing, actúa de manera transversal a las líneas de corriente y permite mejorar la solución numérica alrededor de discontinuidades y otro tipos de fenómenos localizados en el campo de solución de problema. La forma discreta de las ecuaciones de gobierno se completa mediante un esquema de integración temporal explícito de tipo de Runge-Kutta de 4to orden. El esquema de solución básico propuesto se complementa con una técnica de refinamiento adaptativo de malla que permite mejorar automáticamente la solución numérica en zonas localizadas del dominio en que, dadas las características del flujo, se necesita una mayor resolución espacial.Con el propósito de investigar el comportamiento de la formulación numérica se estudian diferentes casos de análisis que implican flujos viscosos y no viscosos en régimen subsónico, transónico y supersónico y se estudia con especial detalle el funcionamiento de la técnica de estabilización propuesta. Los resultados obtenidos demuestran una exactitud satisfactoria y una buena correlación con resultados presentes en la literatura, incluso cuando se trabaja con discretizaciones espaciales relativamente gruesas. Adicionalmente, los estudios numéricos realizados demuestran que el empleo del esquema adaptativo de malla es eficaz para incrementar la exactitud de la solución numérica manteniendo un bajo coste computacional.En la segunda parte de este estudio se propone un método para la optimización de formas aerodinámicas que combina algoritmos genéticos multi-objetivo (MOGAs) y remallado adaptativo con el objetivo de asegurar, con un coste computacional mínimo, la calidad de la solución numérica empleada en el proceso de búsqueda de un determinado diseño objetivo, particularmente cuando el flujo presenta discontinuidades y gradientes muy localizados, típicos de flujos a alta velocidad. La metodología se aplica a resolver tres problemas prácticos de diseño de perfiles aerodinámicos en flujo transónico que implican la optimización de la distribución de presiones, minimización de la resistencia de onda y maximización conjunta de la sustentación y la relación sustentación/resistencia. Para cada uno de ellos se estudia el efecto del refinamiento en la calidad de la solución numérica así como también en el coste computacional y la convergencia del problema. Los estudios realizados demuestran la eficacia de la metodología propuesta.

    This work covers a contribution to two most interesting research elds in aerodynamics, the fi nite element analysis of high-speed compressible flows (Part I) and aerodynamic shape optimization (Part II). The fi rst part of this study aims at the development of a new stabilization formulation based on the Finite Increment Calculus (FIC) scheme for the Euler and Navier-Stokes equations in the context of the Galerkin nite element method (FEM). The FIC method is based on expressing the balance of fluxes in a spacetime domain of nite size. It is tried to prevent the creation of instabilities normally presented in the numerical solutions due to the high convective term and sharp gradients. In order to overcome the typical instabilities happening in the numerical solution of the high-speed compressible flows, two stabilization terms, called streamline term and transverse term, are added through the FIC formulation in space-time domain to the original conservative equations of mass, momentum and energy. Generally, the streamline term holding the direction of the velocity is responsible for stabilizing the spurious solutions produced from the convective term while the transverse term smooths the solution in the high gradient zones. An explicit fourth order Runge-Kutta scheme is implemented to advance the solution in time. In order to investigate the capability of the proposed formulation, some numerical test examples corresponding to subsonic, transonic and supersonic regimes for inviscid and viscous flows are presented. The behavior of the proposed stabilization technique in providing appropriate solutions has been studied especially near the zones where the solution has some complexities such as shock waves, boundary layer, stagnation point, etc. Although the derived methodology delivers precise results with a nearly coarse mesh, the mesh refinement technique is coupled in the solution to create a suitable mesh particularly in the high gradient zones. The comparison of the numerical results obtained from the FIC formulation with the reference ones demonstrates the robustness of the proposed method for stabilization of the Euler and Navier-Stokes equations. It is observed that the usual oscillations occur in the Galerkin FEM, especially near the high gradient zones, are cured by implementing the proposed stabilization terms. Furthermore, allowing the adaptation framework to modify the mesh, the quality of the results improves signi cantly. The second part of this thesis proposes a procedure for aerodynamic shape optimization combining Genetic Algorithm (GA) and mesh re nement technique. In particular, it is investigated the e ect of mesh re nement on the computational cost and solution accuracy during the process of aerodynamic shape optimization. Therefore, an adaptive remeshing technique is joined to the CFD solver for the analysis of each design candidate to guarantee the production of more realistic solutions during the optimum design process in the presence of shock waves. In this study, some practical transonic airfoil design problems using adap- tive mesh techniques coupled to Multi-Objective Genetic Algorithms (MOGAs) and Euler flow analyzer are addressed. The methodology is implemented to solve three practical design problems; the fi rst test case considers a reconstruction design optimization that minimizes the pressure error between a prede ned pressure curve and candidate pressure distribution. The second test considers the total drag minimization by designing airfoil shape operating at transonic speeds. For the final test case, a multi-objective design optimization is conducted to maximize both the lift to drag ratio (L/D) and lift coe cient (Cl). The solutions obtained with and without adaptive mesh re nement are compared in terms of solution accuracy and computational cost. These design problems under transonic speeds need to be solved with a ne mesh, particularly near the object, to capture the shock waves that will cost high computational time and require solution accuracy. By comparison of the the numerical results obtained with both optimization problems, the obtainment of direct bene ts in the reduction of the total computational cost through a better convergence to the final solution is evaluated. Indeed, the improvement of the solution quality when an adaptive remeshing technique is coupled with the optimum design strategy can be judged.

    El presente trabajo pretende contribuir a dos de los campos de investigaci on m as interesantes en la aerodin amica, el an alisis num erico de flujos compresibles a alta velocidad (Parte I) y la optimizaci on de la forma aerodin amica (Parte II). La primera parte de este estudio se centra en la soluci on num erica de las ecuaciones de Navier-Stokes, que modelan el comportamiento de flujos compresibles a alta velocidad. La discretizaci on espacial se lleva a cabo mediante el m etodo de elementos nitos (FEM) y se pone especial enfasis en el desarrollo de una nueva formulaci on estabilizada basada en la t ecnica de c alculo de Incremento fi nitos (FIC). En este ultima, los t erminos de estabilizaci on convectiva se obtienen de manera natural de las ecuaciones de gobierno a trav es de postulados de conservaci on y equilibrio de flujos en un dominio espacio-tiempo de tamaño nito. Ello lleva a la obtenci on de dos t erminos de estabilizaci on que funcionan de manera complementaria. Uno act ua en direcci on de las lineas de corriente proporcionando la estabilizaci on necesaria para contrarestrar las inestabilidades propias de la forma discreta de Galerkin y el otro t ermino, de tipo shock capturing, act ua de manera transversal a las l neas de corriente y permite mejorar la soluci on num erica alrededor de discontinuidades y otro tipos de fen omenos localizados en el campo de soluci on de problema. La forma discreta de las ecuaciones de gobierno se completa mediante un esquema de integraci on temporal expl icito de tipo de Runge-Kutta de 4to orden. El esquema de soluci on b asico propuesto se complementa con una t ecnica de re namiento adaptativo de malla que permite mejorar autom aticamente la soluci on num erica en zonas localizadas del dominio en que, dadas las caracter sticas del flujo, se necesita una mayor resoluci on espacial. Con el prop osito de investigar el comportamiento de la formulaci on num erica se estudian diferentes casos de an alisis que implican flujos viscosos y no viscosos en r egimen subs onico, trans onico y supers onico y se estudia con especial detalle el funcionamiento de la t ecnica de estabilizaci on propuesta. Los resultados obtenidos demuestran una exactitud satisfactoria y una buena correlaci on con resultados presentes en la literatura, incluso cuando se trabaja con discretizaciones espaciales relativamente gruesas. Adicionalmente, los estudios num ericos realizados demuestran que el empleo del esquema adaptativo de malla es e ficaz para incrementar la exactitud de la soluci on numerica manteniendo un bajo coste computacional. En la segunda parte de este estudio se propone un m etodo para la optimizaci on de formas aerodin amicas que combina algoritmos gen eticos multiobjetivo (MOGAs) y remallado adaptativo con el objetivo de asegurar, con un coste computacional m nimo, la calidad de la soluci on numerica empleada en el proceso de b usqueda de un determinado diseño objetivo, particularmente cuando el flujo presenta discontinuidades y gradientes muy localizados, ti picos de flujos a alta velocidad. La metodolog a se aplica a resolver tres problemas pr acticos de diseño de per les aerodin amicos en flujo trans onico que implican la optimizaci on de la distribuci on de presiones, minimizaci on de la resistencia de onda y maximizaci on conjunta de la sustentaci on y la relaci on sustentaci on/resistencia. Para cada uno de ellos se estudia el efecto del re namiento en la calidad de la soluci on num erica as como tambi en en el coste computacional y la convergencia del problema. Los estudios realizados demuestran la e cacia de la metodolog a propuesta.

  • Advances in the development of a FEM model for evaluation of a surface effect ship including skirt dynamics

     Garcia Espinosa, Julio; Serván Camas, Borja; Di Capua, Daniel; Ubach Fuentes, Pere-Andreu; Oñate Ibáñez de Navarra, Eugenio
    New frontiers (SNAMES Annual Journal)
    Date of publication: 2013-06-01
    Journal article

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    This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of a SES including skirt dynamics. In this work, a potential flow approach along with a stream-line integration of the free surface is used. The paper focuses on the fluid-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 algorithm is based, on one side, on a staggered explicit algorithm, using a TCP/IP sockets link, able to communicate 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. Several cases of the XR-1B T-Craft model have been studied to demonstrate the developed algorithm.

  • A four-noded quadrilateral element for composite laminated plates/shells using the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    International journal for numerical methods in engineering
    Date of publication: 2013-05-20
    Journal article

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    A new bilinear four-noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory is presented. The element has seven kinematic variables per node. Shear locking is avoided by introducing an assumed linear shear strain field. The performance of the element is studied in several examples where the reference solution is the 3D finite element analysis using 20-noded hexahedral elements.

    A new bilinear four-noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory is presented. The element has seven kinematic variables per node. Shear locking is avoided by introducing an assumed linear shear strain field. The performance of the element is studied in several examples where the reference solution is the 3D finite element analysis using 20-noded hexahedral elements.

  • Analysis of the melting, burning and flame spread of polymers with the particle finite element method

     Oñate Ibáñez de Navarra, Eugenio; Marti, Julio Marcelo; Ryzhakov, Pavel; Rossi, Riccardo; Idelsohn Barg, Sergio Rodolfo
    Computer Assisted Methods in Engineering and Science
    Date of publication: 2013
    Journal article

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    A computational procedure for analysis of the melting, burning and flame spread of polymers under fire conditions is presented. The method, termed particle finite element method (PFEM), combines concepts from particle-based techniques with those of the standard finite element method (FEM). The key feature of the PFEM is the use of an updated Lagrangian description to model the motion of nodes (particles) in the thermoplastic material. Nodes are viewed as material points which can freely move and even separate from the main analysis domain representing, for instance, the effect of melting and dripping of polymer particles. A mesh connects the nodes defining the discretized domain where the governing equations are solved using the FEM. An incremental iterative scheme for the solution of the nonlinear transient coupled thermal-flow problem, including radiation, loss of mass by gasification and combustion is used. Examples of the possibilities of the PFEM for the modelling and simulation of the melting, burning and flame spread of polymers under different fire conditions are described.

  • A numerical model of delamination in composite laminated beams using the LRZ beam element based on the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Composite structures
    Date of publication: 2013-10
    Journal article

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    A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum isotropic damage model [2]. The modified Newton-Raphson method is used for solving the non-linear problem.The RZT theory, the LRZ finite element and the isotropic damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.

    A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum isotropic damage model [2]. The modified Newton–Raphson method is used for solving the non-linear problem. The RZT theory, the LRZ finite element and the isotropic damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.

  • Robust design optimisation of advance hybrid (fiber¿metal) composite structures

     Lee, Dong Seop; Morillo Carbonell, Carlos; Oller Martinez, Sergio Horacio; Bugeda Castelltort, Gabriel; Oñate Ibáñez de Navarra, Eugenio
    Composite structures
    Date of publication: 2013-05
    Journal article

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  • Modelling of tunnelling processes and rock cutting tool wear with the particle finite element method

     Carbonell Puigbo, Josep Maria; Oñate Ibáñez de Navarra, Eugenio; Suarez Arroyo, Benjamin
    Computational Mechanics
    Date of publication: 2013-09-13
    Journal article

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    Underground construction involves all sort of challenges in analysis, design, project and execution phases. The dimension of tunnels and their structural requirements are growing, and so safety and security demands do. New engineering tools are needed to perform a safer planning and design. This work presents the advances in the particle finite element method (PFEM) for the modelling and the analysis of tunneling processes including the wear of the cutting tools. The PFEM has its foundation on the Lagrangian description of the motion of a continuum built from a set of particles with known physical properties. The method uses a remeshing process combined with the alpha-shape technique to detect the contacting surfaces and a finite element method for the mechanical computations. A contact procedure has been developed for the PFEM which is combined with a constitutive model for predicting the excavation front and the wear of cutting tools. The material parameters govern the coupling of frictional contact and wear between the interacting domains at the excavation front. The PFEM allows predicting several parameters which are relevant for estimating the performance of a tunnelling boring machine such as wear in the cutting tools, the pressure distribution on the face of the boring machine and the vibrations produced in the machinery and the adjacent soil/rock. The final aim is to help in the design of the excavating tools and in the planning of the tunnelling operations. The applications presented show that the PFEM is a promising technique for the analysis of tunnelling problems. © 2013 Springer-Verlag Berlin Heidelberg.

  • Advances in the development of a FEM model for evaluation of a Surface-Effect Ship (SES) including skirt dynamics

     Garcia Espinosa, Julio; Serván Camas, Borja; Di Capua, Daniel; Ubach Fuentes, Pere-Andreu; Oñate Ibáñez de Navarra, Eugenio
    Ingeniería naval
    Date of publication: 2013-12-01
    Journal article

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    The Innovative Naval Prototype Transformable Craft (T-Craft) is a novel United States Navy concept for a seabase-to-shore connector, operative in multiple modes. It can self deploy from an intermediate support base to the sea base and then be used as a high speed connector from the sea base to the shore, transporting wheeled and tracked vehicles and other heavy equipment and cargo through the surf zone and onto the beach,where it can discharge its cargo without the need for a port. T-Craft has been conceived as a surface-effect ship (SES) with a fanactivated air cushion between two rigid hulls, allowing the vessel to operate in modes of full displacement, partial air-cushion support, and full aircushion support. This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of a T-Craft seakeeping and maneuvering, including skirt dynamics. In this work, a potential flow approach along with a stream-line integration of the free surface is used. The paper focuses on the fluid-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 algorithm is based, on one side, on a staggered explicit algorithm, using a TCP/IP sockets link, able to communicate 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. Several cases of the XR-1B T-Craft model have been studied to demonstrate the developed algorithm. This research has been sponsored by the Office of Naval Research under Grant N62909-10-1-7053.

  • Characterization of mechanical properties of biological tissue: application to the FEM analysis of the urinary bladder

     Oñate Ibáñez de Navarra, Eugenio; Bellomo, Facundo J.; Monteiro, Virginia; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Date of publication: 2013
    Book chapter

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    This text presents an approach for the mechanical behavior of soft biological tissue using the finite elements method and a general constitutive model. Specifically we analyze the mechanical behavior of a urinary bladder starting from a procedure for obtaining the mechanical characterization of the biological tissue. Bladder tissue is modelled as a composite material formed by soft matrix reinforced with preferentially oriented fibres. In the first part of the text we present a procedure for identifying the mechanical properties of biological tissue main constituents by an inverse method. Then this information is used for the numerical simulation of the mechanical behavior of the bladder within the FEM. The formulation can be applied to various types of biological tissues, both in the field of material characterization, and in the numerical simulation of the tissue biomechanical behavior.

  • The particle finite element method (PFEM): an effective numerical technique for solving marine, naval and harbour engineering problems

     Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Celigueta Jordana, Miguel Angel; Suarez Arroyo, Benjamin
    Date of publication: 2013-05-02
    Book chapter

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    Being capable of predicting wave-structure interaction in the time domain is of great interest for the offshore industry. However, most computer programs used in the industry work in the frequency domain. Therefore, the main objective of this work is the development a time domain solver based on the finite element method capable of solving wave-structure interaction problems using unstructured meshes. We found good agreement between the numerical results we obtained and analytical solutions as well as numerical solutions obtained by other numerical method.

    We present some developments in the Particle Finite Element Method (PFEM) for the solution of complex coupled problems in marine, naval and harbour engineering involving fluid-soil-structure interaction (FSSI). The PFEM uses an updated Lagrangian description to model the motion of nodes (particles) in a continuum domain containing fluid, soil/rock and structures subdomains. A mesh connects the nodes defining the discretized domain where the governing equations for each of the constituent materials are solved with the FEM. The stabilization for dealing with an incompressibility material is introduced via the finite calculus (FIC) method. An incremental iterative scheme for solving the non linear transient FSSI problem is described. The procedure to model frictional contact conditions and material erosion at fluid-solid and solid-solid interfaces is described. We present examples of application of the PFEM to solve FSSI problems in marine, naval and harbour engineering such as the motion of rocks by water streams, the stability of breakwaters and constructions under sea waves, the sinking of ships and the collision of a ship with ice blocks.

  • Access to the full text
    Modelling and simulation of the sea-landing of aerial vehicles using the Particle Finite Element Method  Open access

     Ryzhakov, Pavel; Rossi, Riccardo; Viña, Adria; Oñate Ibáñez de Navarra, Eugenio
    Ocean engineering
    Date of publication: 2013-07
    Journal article

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    In this paper the Particle Finite Element Method (PFEM) is applied to the simulation of the sea-landing of an unmanned aerial vehicle (UAV). The problem of interest consists in modelling the impact of the vehicle against the water surface, analyzing the main kinematic and dynamic quantities (such as loads exerted upon the capsule at the moment of the impact). The PFEM, a methodology well-suited for free-surface flow simulation is used for modelling the water while a rigid body model is chosen for the vehicle. The vehicle under consideration is characterized by low weight. This leads to difficulties in modelling the fluid¿structure interaction using standard Dirichlet¿Neumann coupling. We apply a modified partitioned strategy introducing the interface Laplacian into the pressure Poisson's equation for obtaining a convergent FSI solution. The paper concludes with an industrial example of a vehicle sea-landing modelled using PFEM.

    In this paper the Particle Finite Element Method (PFEM) is applied to the simulation of the sea-landing of an unmanned aerial vehicle (UAV). The problem of interest consists in modelling the impact of the vehicle against the water surface, analyzing the main kinematic and dynamic quantities (such as loads exerted upon the capsule at the moment of the impact). The PFEM, a methodology well-suited for free-surface flow simulation is used for modelling the water while a rigid body model is chosen for the vehicle. The vehicle under consideration is characterized by low weight. This leads to difficulties in modelling the fluid–structure interaction using standard Dirichlet–Neumann coupling. We apply a modified partitioned strategy introducing the interface Laplacian into the pressure Poisson's equation for obtaining a convergent FSI solution. The paper concludes with an industrial example of a vehicle sea-landing modelled using PFEM.

  • On the theory of cell migration: durotaxis and chemotaxis  Open access

     Diego Iñiguez, Javier
    Defense's date: 2013-07-03
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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    La migracio cel.lular es fonamental en molts processos fisiologics i patologics. Alteracio dels seus mecanismes regulatoris comporta perdues d'adherencia i augment de motilitat, critiques en les etapes incials de la metastasi. Per tant, la migracio cel.lular ha esdevingut un camp intensiu de recerca experimental i teorica, pero la comprensio dels mecanismes que la governen es incompleta. La migracio cel.lular es resultat d'una sequencia periodica d'etapes de protrusio, remodelacio d'adhesions i contraccio que permet el moviment dirigit cap a estimuls externs. La coordinacio espai-temporal d'aquests processos depen de l'activacio de xarxes de senyalitzacio a localizacions subcel.lulars especifiques. La familia de les RhoGTPases es particularment important en la regulacio de la polarizacio, formacio d'adhesions i generacio de forces propulsores del moviment cel.lular. Models teorics basats en una descripcio independent d'aquests processos tenen una capacitat limitada de predir el comportament cel.lular observat in vitro, perque la seva funcionalitat depen de l'acoblament de les xarxes reguladores que els governen. Aquesta Tesi presenta un model que integra una descripcio de la generacio de forces i deformacio cel.lular, dinamica d'adhesions i activacio de les RhoGTPAses. La cel.lula es modelada com un solid viscoelastic actiu amb capacitat de generar forces de protrusio i contraccio. Les forces estan determindades pel nivel d'activacio de les RhoGTPases, la distribucio de les quals esta governada per un sistema d'equacions de Reaccio-Difusio. Les adhesion Focals es modelen com clusters de receptors transmembrana que s'enllacen dinamicament amb la matriu extracel.lular depenent de les forces transmeses i la distancia entre els receptors i els lligands en el substracte.A nivell teoric, un resultat important relaciona la topologia d'un Graf d¿Interaccio i les propietats de la xarxa de reaccio associada com a sistema de regulacio i deteccio de gradients: polarizacio reversible, adaptacio a estimuls homogenis, resposta a estimuls simultanis i amplificacio. Models formulats d¿acord a aquests principis son robustos davant la variabilitat biologica associada a diferents tipus de cel.lules i capturen el comportament observat en experiments de Chemotaxis: la capacitat de detectar gradients febles, polaritzar sense generar patrons Turing d¿activacio, i alterar la direccio de migracio quan la font de l¿estimul canvia. Les implicacions biologiques d¿aquests models suggereixen que el paper generalment acceptat dels GEFs, GAPs i GDIs en la interaccio de les RhoGTPases s¿ha de revisar, tal com recolza evidencia experimental recent. El model permet reproduir la transicio entre la forma carateristica de neutrophiles i keratocytes adoptades durant la migracio, variant les magnituds de les forces de contraccio i protrusio o, alternativament, la intensitat de la interaccio entre RhoGTPases. El darrer mecanisme es una explicio novedosa de les diferents morfologies cel.lulars observades durant la migracio.Sobre mechano-sensing, es proposa una nova hipotesi per explicar com les cel.lules detecten les propietats mecaniques de la ECM. La hipotesi proporciona una explicacio unificadora a mesures aparenment contradictories de desenvolupament de forces i creixement d¿adhesion focals, previament atribuides a diferencies en els muntages experimentals o tipus cel.lulars estudiats. Una interpretacio de les relacions observades entre temps de polaritzacio, velocitat de migracio, limits de mecano-sensibilitat i la rigidesa del susbtracte es deriva d¿aquesta hipotesi. Finalment, la teoria suggereix els mecanismes, actualment desconeguts, que podrien explicar la preferencia universal de les cel.lules (exceptuant neurones) a migrar al llarg de gradients de rigidesa i, per primera vegada, una funcio biologica plausible per l¿existencia d¿aquest fenomen. Es coneix com Durotaxis, i la seva desregulacio ha estat associada al comportament de cel.lules cancerigenes.

    Cell migration is a fundamental element in a variety of physiological and pathological processes. Alteration of its regulatory mechanisms leads to loss of adhesion and increased motility, critical steps in the initial stages of metastasis. Consequently, cell migration has become the focus of intensive experimental and theoretical studies; however the understanding many of its mechanisms remains elusive. Cell migration is the result of a periodic sequence of protrusion, adhesion remodeling and contraction stages that leads to directed movement towards external stimuli. The spatio-temporal coordination of these processes depends on the activation of the signaling networks that regulate them at specific subcellular locations. Particularly, the family of small RhoGTPases plays a central role in regulating cell polarization, the formation of adhesion sites and the generation of the forces that drive motion. Theoretical models based on an independent description of these processes have a limited capacity to predict cellular behavior observed in vitro, since their functionality depends on the cross-regulation between their signaling pathways. This thesis presents a model of cell migration that integrates a description of force generation and cell deformation, adhesion site dynamics and RhoGTPases activation. The cell is modeled as a viscoelastic body capable of developing traction and protrusion forces. The forces are determined by the activation level of the RhoGTPases, whose distribution in the cell is described by a set of reaction-diffusion equations. Adhesion sites are modeled as punctual clusters of transmembrane receptors that dynamically bind and unbind the extracellular matrix depending on the force transimtted to them and the distance with ligands coating the substrate. On the theoretical level, the major findings relate the topology of a Crosstalk Scheme and the properties inherited by the associated reaction network as a gradient sensing and regulatory system: reversible polarization, adaptation to uniform stimulus, multi-stimuli response and amplification. Models formulated according to these principles remain functional against the biological diversity associated to different cell types and match the observed behavior in Chemotaxis essays: the capacity of cells to detect shallow gradients, polarize without featuring Turing patterns of activation, and switch the direction of migration after the stimulus source is changed. The biological implications challenge a long held view on the mechanisms of RhoGTPase crosstalk and suggests that the role of GDIs, GEFs and GAPs has to be revised, as supported by recent experimental evidence. In addition, the model recapitulates a continuous transition from the tear-like shape adopted by neutrophiles to the fan-like shape of keratocytes during migration by varying the magnitudes of protrusion and contraction forces or, alternatively, the strength of RhoGTPase Crosstalk. The second mechanism represents a novel explanation of the different morphologies observed in migrating cells. On cell mechanosensing, a new hypothesis is proposed to explain how cells sense the mechanical properties of the ECM. The hypothesis provides a unifying explanation to apparently conflicting observations on force development and growth in real time at cell Focal adhesions, previously attributed to differences in experimental set-ups or cell types studied. An interpretation for the observed relationships between polarization time, migration speed, mechano-sensing limits and substrate rigidity follows from this hypothesis. Further, the theory directly suggests the currently unknown mechanisms that could explain the universal preference of cells (bar neurons) to migrate along stiffness gradients, and for the first time, a plausible biological function for the existence of this phenomenon. It is known as Durotaxis, and its abnormal regulation has been associated to the malignant behaviour of cancer cells.

  • Computational Model of the Human Urinary Bladder  Open access

     Silva Araujo monteiro, Virginia
    Defense's date: 2013-06-10
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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    La propuesta de una vejiga artificial es un obstáculo a trasponer. El cáncer de vejiga está entrelos casos más frecuentes de enfermedades oncológicas en Estados Unidos y Europa. Ese cánceres considerado un problema médico importante una vez que esa enfermedad presenta altastasas de re-ocurrencia, muchas veces llevando a la remoción del órgano.La solución más sofisticada para remplazar ese órgano es la vejiga ileal, que consiste en una neovejigahecha de tejido intestinal del enfermo. Desafortunadamente, esa solución presenta no soloproblemas mecánicos funcionales, descritos en la literatura como problemas de vaciado y fuga,peo también problemas de orden biológica (como ejemplo pérdida ósea, debido a la absorciónpor el intestino de substancias que necesitan ser eliminadas del organismo).A través de la solicitación de la comunidad urológica del Hospital Clínico de Barcelona y con suexperiencia en modelos numéricos para estructuras biomédicas, el Centro de MétodosNuméricos en Ingeniería (CIMNE) ha tenido la iniciativa de proporcionar actividadinvestigadora de la mecánica de la vejiga urinaria y de la simulación de interacción fluidoestructurapara reproducir el llenado y vaciado de ese órgano con la orina.La simulación de la vejiga humana por el Método de los Elementos Finitos (FEM) y un completoentendimiento de la mecánica de ese órgano y de su interacción con la orina dará la posibilidadde proponer mejora en la geometría y de analizar materiales para la solución artificial en caso deremplazamiento de la vejiga.Para lograr ese objetivo, primeramente procedemos a una revisión bibliográfica de los modelosmatemáticos del aparato urinario y un estudio comprehensivo de la fisiología y dinámica de lavejiga. Presentamos una revisión de las principales estructuras urológicas, riñón, uréter y uretra.Las estructuras anexas también son consideradas para entender las condiciones de contorno delproblema estudiado.Posteriormente, proponemos el modelo constitutivo para estudiar la vejiga urinaria humana. Elcomportamiento del musculo detrusor durante llenado y vaciado de la vejiga con orina, suhabilidad de retención de orina a baja presión debe ser correctamente representada por mediode la implementación de un modelo constitutivo no-lineal. El modelo matemático necesitarepresentar las variables mecánicas que gobiernan ese órgano, y también las propiedades de laorina. El comportamiento no-lineal de tejidos vivos es implementado y validado con ejemplos dela literatura. La propiedad quasi-incompressible de la orina y las ecuaciones Navier-Stokes sonconsideradas para análisis del fluido.Para representar la geometría de la vejiga, implementamos un modelo computacional 3D apartir de imágenes de tomografía computadorizada de un cadáver adulto. Los datos son tratadospara considerar las condiciones de contorno. Hemos construido dos modelos de malla: ummallado com tetrahedos de quatro nodos y outro mallado com elementos de membrana de tresnodos.El esquema utilizado para calcular la interacción fluido-estructura debe ser adecuado paramateriales de densidad muy parecidas. La análisis numérica de llenado y vaciado de la vejigahumana es validada con testes urodinámicos estandarizados.La parte final de la tesis, presentamos una simulación de una neo-vejiga, siendo el primer pasopara representar numéricamente materiales artificiales para remplazamiento de la vejiga

    La propuesta de una vejiga artificial es un obstáculo a trasponer. El cáncer de vejiga está entre los casos más frecuentes de enfermedades oncológicas en Estados Unidos y Europa. Ese cáncer es considerado un problema médico importante una vez que esa enfermedad presenta altas tasas de re-ocurrencia, muchas veces llevando a la remoción del órgano. La solución más sofisticada para remplazar ese órgano es la vejiga ileal, que consiste en una neovejiga hecha de tejido intestinal del enfermo. Desafortunadamente, esa solución presenta no solo problemas mecánicos funcionales, descritos en la literatura como problemas de vaciado y fuga, peo también problemas de orden biológica (como ejemplo pérdida ósea, debido a la absorción por el intestino de substancias que necesitan ser eliminadas del organismo). A través de la solicitación de la comunidad urológica del Hospital Clínico de Barcelona y con su experiencia en modelos numéricos para estructuras biomédicas, el Centro de Métodos Numéricos en Ingeniería (CIMNE) ha tenido la iniciativa de proporcionar actividad investigadora de la mecánica de la vejiga urinaria y de la simulación de interacción fluidoestructura para reproducir el llenado y vaciado de ese órgano con la orina. La simulación de la vejiga humana por el Método de los Elementos Finitos (FEM) y un completo entendimiento de la mecánica de ese órgano y de su interacción con la orina dará la posibilidad de proponer mejora en la geometría y de analizar materiales para la solución artificial en caso de remplazamiento de la vejiga. Para lograr ese objetivo, primeramente procedemos a una revisión bibliográfica de los modelos matemáticos del aparato urinario y un estudio comprehensivo de la fisiología y dinámica de la vejiga. Presentamos una revisión de las principales estructuras urológicas, riñón, uréter y uretra. Las estructuras anexas también son consideradas para entender las condiciones de contorno del problema estudiado. Posteriormente, proponemos el modelo constitutivo para estudiar la vejiga urinaria humana. El comportamiento del musculo detrusor durante llenado y vaciado de la vejiga con orina, su habilidad de retención de orina a baja presión debe ser correctamente representada por medio de la implementación de un modelo constitutivo no-lineal. El modelo matemático necesita representar las variables mecánicas que gobiernan ese órgano, y también las propiedades de la orina. El comportamiento no-lineal de tejidos vivos es implementado y validado con ejemplos de la literatura. La propiedad quasi-incompressible de la orina y las ecuaciones Navier-Stokes son consideradas para análisis del fluido. Para representar la geometría de la vejiga, implementamos un modelo computacional 3D a partir de imágenes de tomografía computadorizada de un cadáver adulto. Los datos son tratados para considerar las condiciones de contorno. Hemos construido dos modelos de malla: un mallado con tetrahedos de cuatro nodos y otro mallado con elementos de membrana de tres nodos. El esquema utilizado para calcular la interacción fluido-estructura debe ser adecuado para materiales de densidad muy parecidas. El análisis numérico de llenado y vaciado de la vejiga humana es validada con tests urodinámicos estandarizados. La parte final de la tesis, presentamos una simulación de una neo-vejiga, siendo el primer paso para representar numéricamente materiales artificiales para remplazamiento de la vejiga.

    The proposal of an artificial bladder is still a challenge to overcome. Bladder cancer is among the most frequent cases of oncologic diseases in United States and Europe. It is considered a major medical problem once this disease has high rates of reoccurrence, often leading to the extirpation of this organ. The most refined solution to replace this organ is the ileal bladder, which consists of a neobladder made of the patient’s intestinal tissue. Unfortunately this solution presents not only functional mechanical problems, described on the literature as voiding and leaking problems, but also biological ones (i.e. bone loss, given the absorption by the intestine of substances that should be eliminated from the organism). Urged by the urological community of the Hospital Clinic de Barcelona and backgrounded by its experience in the numerical simulation of biomedical structures, the Center of Numerical Methods in Engineering (CIMNE) had the initiative to provide the research of the mechanics of the urinary bladder and the simulation of fluid structure interaction (FSI) to account for the filling and voiding of this organ with urine. The Finite Element Method (FEM) simulation of the real bladder and the comprehensive understanding of the mechanics of this organ and its interaction with urine will give the possibility to propose geometrical improvements and study suitable materials for an artificial solution to address the cases on which the bladder needs to be removed. To reach this goal, first we proceeded to the bibliographic review of mathematical models of the urinary apparatus and to a comprehensive study of the physiology and dynamics of the bladder. A review of the major urological structures, kidney, ureter and urethra, takes place. To consider boundary conditions other surrounding structures to the urinary system are also studied. In the second part of the thesis, we propose the numerical model to study the human urinary bladder. The behavior of the detrusor muscle during filling and voiding of the bladder with urine and its ability to promote the storage of urine under low pressure need to be accurately represented, requiring the implementation of a non-linear constitutive model. The mathematical model needs to be capable to simulate the mechanical variables that govern this organ and the properties of the urine. The nonlinear behavior of living tissues is implemented and validated with examples from the literature. The quasi-incompressibility property of urine and the navierstokes equations for the fluid are taken into account. The geometry of the bladder needs to be taken into account, and the implementation of a 3D computational model obtained from the computerized tomography of a cadaver male adult is considered. The data has been treated to consider boundary conditions. Two models have been conceived: one meshed with four nodes tetrahedral and another meshed with shell elements. FSI must work for the simulation of filling and voiding of the bladder. Due to the close densities of the materials the scheme used to solve fluid-structure needs to be carefully selected. The proposed numerical model and the filling and voiding analysis are finally validated with standardized urodynamic tests. The final part of the thesis, the simulation of a neobladder is presented, being the first step to simulate numerically artificial materials for bladder replacement.

  • A compressible lagrangian framework for the simulation of underwater implosion problems  Open access

     Kamran, Kazem
    Defense's date: 2013-06-21
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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    El desarrollo de métodos eficientes para modelar la dinámica de implosión presenta varios desafíos. El primero es una representación eficaz de la dinámica del sistema acoplado de aire-agua. El segundo es que el método tiene que permitir una detección exacta o un seguimiento adecuado de la interfase entre ambas fases. Por último el método tiene que ser capaz de resolver cualquier choque que podría generar en el aire o en el agua, sobre todo en la última fase del colapso. Nosotros presentamos un método numérico compresible y totalmente Lagrangiano para simular la implosión bajo el agua. Tanto el aire como el agua se consideran compresibles y las ecuaciones Lagrangianos para la hidrodinámica del choque se estabilizan mediante un método multiescala que es variacionalmente consistente. Se utiliza una definición de interfase que coincide perfectamente con los nodos. Ésta, nos facilita duplicar eficazmente las variables cinéticas como la presión y la densidad en los nodos de la interfase. Con el fin de obtener suficiente resolución alrededor de la interfase, la malla se genera de forma adaptativa y respetando la posición de la interfase. A continuación el método desarrollado se utiliza para simular la implosión bajo el agua de una burbuja cilíndrica del tamaño de un centímetro. Varios fenómenos se han capturado durante el colapso: un ciclo inmediato de colapso-crecimiento de la burbuja que ocurre en un espacio (0.3 mm) y tiempo (0.1 ms) bastante limitado, aparición de inestabilidades de tipo Rayleigh-Taylor en la interfase y formaron de varias ondas de choque que viajan tanto en el agua como en el aire. Después, seguimos el desarrollo del método para modelar la implosión bajo el agua de un contenedor metálico considerando una interacción monolítica de fluido y estructura. El cilindro de aluminio, que a su vez contiene aire a presión atmosférica y está rodeada de agua en alta presión, se modelando con elementos de lámina de tres nodos y sin grados de libertad de rotación. El cilindro se somete a deformaciones transitorias suficientemente rápidos y enormes hasta llegar a colapsar. Un nuevo modelo elástico de contacto sin considerar la fricción se ha desarrollado para detectar el contacto y calcular las fuerzas en el dominio discretizado entre las superficies medianas de las laminas. Dos esquemas temporales están considerados, uno es implícito utilizando el método de Bossak y otro es explícito utilizando Forward Euler. Al final los resultados de ambos casos se comparan con los resultados experimentales

    The development of efficient algorithms to understand implosion dynamics presents a number of challenges. The foremost challenge is to efficiently represent the coupled compressible fluid dynamics of internal air and surrounding water. Secondly, the method must allow one to accurately detect or follow the interface between the phases. Finally, it must be capable of resolving any shock waves which may be created in air or water during the final stage of the collapse. We present a fully Lagrangian compressible numerical framework for the simulation of underwater implosion. Both air and water are considered compressible and the equations for the Lagrangian shock hydrodynamics are stabilized via a variationally consistent multiscale method [109]. A nodally perfect matched definition of the interface is used [57, 25] and then the kinetic variables, pressure and density, are duplicated at the interface level. An adaptive mesh generation procedure, which respects the interface connectivities, is applied to provide enough refinement at the interface level. This framework is then used to simulate the underwater implosion of a large cylindrical bubble, with a size in the order of cm. Rapid collapse and growth of the bubble occurred on very small spatial (0.3mm), and time (0.1ms) scales followed by Rayleigh-Taylor instabilities at the interface, in addition to the shock waves traveling in the fluid domains are among the phenomena that are observed in the simulation. We then extend our framework to model the underwater implosion of a cylindrical aluminum container considering a monolithic fluid-structure interaction (FSI). The aluminum cylinder, which separates the internal atmospheric-pressure air from the external high-pressure water, is modeled by a three node rotation-free shell element. The cylinder undergoes fast transient deformations, large enough to produce self-contact along it. A novel elastic frictionless contact model is used to detect contact and compute the non-penetrating forces in the discretized domain between the mid-planes of the shell. Two schemes are tested, implicit using the predictor/multi-corrector Bossak scheme, and explicit, using the forward Euler scheme. The results of the two simulations are compared with experimental data.

    El desarrollo de métodos eficientes para modelar la dinámica de implosión presenta varios desafíos. El primero es una representación eficaz de la dinámica del sistema acoplado de aire-agua. El segundo es que el método tiene que permitir una detección exacta o un seguimiento adecuado de la interfase entre ambas fases. Por último el método tiene que ser capaz de resolver cualquier choque que podría generar en el aire o en el agua, sobre todo en la última fase del colapso. Nosotros presentamos un método numérico compresible y totalmente Lagrangiano para simular la implosión bajo el agua. Tanto el aire como el agua se consideran compresibles y las ecuaciones Lagrangianos para la hidrodinámica del choque se estabilizan mediante un método multiescala que es variacionalmente consistente [109]. Se utiliza una definición de interfase que coincide perfectamente con los nodos [57, 25]. Ésta, nos facilita duplicar eficazmente las variables cinéticas como la presión y la densidad en los nodos de la interfase. Con el fin de obtener suficiente resolución alrededor de la interfase, la malla se genera de forma adaptativa y respetando la posición de la interfase. A continuación el método desarrollado se utiliza para simular la implosión bajo el agua de una burbuja cilíndrica del tamaño de un centímetro. Varios fenómenos se han capturado durante el colapso: un ciclo inmediato de colapso-crecimiento de la burbuja que ocurre en un espacio (0.3mm) y tiempo (0.1ms) bastante limitado, aparición de inestabilidades de tipo Rayleigh-Taylor en la interfase y formaron de varias ondas de choque que viajan tanto en el agua como en el aire. Después, seguimos el desarrollo del método para modelar la implosión bajo el agua de un contenedor metálico considerando una interacción monolítica de fluido y estructura. El cilindro de aluminio, que a su vez contiene aire a presión atmosférica y está rodeada de agua en alta presión, se modelando con elementos de lámina de tres nodos y sin grados de libertad de rotación. El cilindro se somete a deformaciones transitorias suficientemente rápidos y enormes hasta llegar a colapsar. Un nuevo modelo elástico de contacto sin considerar la fricción se ha desarrollado para detectar el contacto y calcular las fuerzas en el dominio discretizado entre las superficies medianas de las laminas. Dos esquemas temporales están considerados, uno es implícito utilizando el método de Bossak y otro es explícito utilizando Forward Euler. Al final los resultados de ambos casos se comparan con los resultados experimentales.

  • The Particle Finite Element Method (PFEM): an effective numerical technique for solving coastal engineering problems

     Oñate Ibáñez de Navarra, Eugenio; Celigueta Jordana, Miguel Angel; Idelsohn Barg, Sergio Rodolfo
    International Conference on Discrete Element Methods and Related Techniques
    Presentation's date: 2013-08-06
    Presentation of work at congresses

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    Conditioning of network impedance by insertion of a virtual inductance as an inherent feature of the converter control system has the potential to extend the range of stable operation of the overall system. This paper presents a scenario in which such potential is explored and its range of application is identified. It shows first that implementation of a virtual inductance is naturally suited for combination with Virtual Flux-based control systems, and that it can be extended to the more general case of a virtual reactance. The paper then presents the structure of a control system for operation under unbalanced conditions, where the virtual inductance directly influences the current reference calculation. Compared with the standard approach of unity power factor control of grid integrated converters, the suggested technique allows for improving the stability range of converters operating in high-impedance grids, and for remote point control of reactive power or power factor.

  • Simulation of particles transport in fluids with the particle finite element method: application to drilling cuttings in wellbores.

     Celigueta Jordana, Miguel Angel; Deshpande, Kedar M.; Miquel Canet, Juan; Latorre Sánchez, Salvador; Ubach Fuentes, Pere-Andreu; Oñate Ibáñez de Navarra, Eugenio
    Congress on Numerical Methods in Engineering
    Presentation's date: 2013-06-27
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  • Diseño óptimo multi-objetivo y ecológico de materiales con estructuras compuestas con nanotubos de carbono

     Morillo, Carlos; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    Congreso de Métodos Numéricos en Ingeniería
    Presentation's date: 2013-06-26
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  • A parallel partitioning method for discrete element methods

     Dadvand, Pooyan; Roig, C.; Oñate Ibáñez de Navarra, Eugenio
    Congreso de Métodos Numéricos en Ingeniería
    Presentation's date: 2013-06-25
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  • Advances in the modelling of excavation and cutting tool wear with the particle finite element method

     Carbonell Puigbo, Josep Maria; Oñate Ibáñez de Navarra, Eugenio; Suarez Arroyo, Benjamin
    International Conference Computational Methods in Tunneling and Subsurface Engineering
    Presentation's date: 2013
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  • A discrete element method for analysis of drilling problems

     Oñate Ibáñez de Navarra, Eugenio; Arrufat Garcia, Ferran; Zarate Araiza, Jose Francisco; Ubach Fuentes, Pere-Andreu
    International Conference on Computational Methods in Marine Engineering
    Presentation's date: 2013-05
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  • Posibilidades de la inteligencia artificial en el análisis de auscultación de presas

     Salazar González, Fernando; Oñate Ibáñez de Navarra, Eugenio; Toledo Municio, Miguel Ángel
    Jornadas de Ingeniería del Agua
    Presentation's date: 2013-10
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  • Modelación física y numérica de aliviaderos con cajeros altamente convergentes

     San Mauro, Javier; Salazar González, Fernando; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio; Morera, l.; Toledo Municio, Miguel Ángel; Morán Moya, Rafael; Caballero, F.J.; Martínez, B.; Guerrero, J.
    Jornadas de Ingeniería del Agua
    Presentation's date: 2013-10
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  • Advances in the development of a FEM model for evaluation of a Surface-Effect Ship (SES) including skirt dynamics

     Garcia Espinosa, Julio; Serván Camas, Borja; Di Capua, Daniel; Ubach Fuentes, Pere-Andreu; Oñate Ibáñez de Navarra, Eugenio
    Congreso de Ingeniería Naval e Industria Marítima
    Presentation's date: 2013-10-24
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    This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of a SES including skirt dynamics. In this work, a potential flow approach along with a stream-line integration of the free surface is used. The paper focuses on the fluid-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 algorithm is based, on one side, on a staggered explicit algorithm, using a TCP/IP sockets link, able to communicate 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. Several cases of the XR-1B SES model have been studied to demonstrate the developed algorithm.

    El “Innovative Naval Prototype Transformable Craft” (T-Craft) es un nuevo concepto de buque desarrollado por la marina de los Estados Unidos de América para la conexión de una base en alta mar con tierra. El TCraft puede operar en múltiple modos, usándose para conectar una base intermedia de soporte con la principal, y luego ser utilizado como conexión de alta velocidad con la costa, transportando vehículos y otros equipos y carga pesada hasta la playa. El T-Craft se ha concebido como un buque de efecto superficie (Surface-Effect Ship, SES) con un colchón de aire activo entre dos cascos rígidos, que permite al buque operar a desplazamiento completo, con soporte parcial del colchón o con el colchón plenamente activo. Este artículo presenta el trabajo reciente de los autores en el desarrollo de un modelo de evaluación del comportamiento en la mar y la maniobrabilidad del T-Craft, incluyendo la interacción del faldón. Este modelo está basado en la resolución de las ecuaciones de flujo potencial en el dominio del tiempo, mediante el método de los elementos finitos, integrando la superficie libre a lo largo de las líneas de corriente. Este artículo revisa el algoritmo de interacción fluido estructura desarrollado para la simulación de la compleja dinámica de los sellos, en la interfaz entre el colchón de aire y el agua. El algoritmo se basa, por una parte, en un algoritmo explícito alternado que permite la comunicación entre los solvers fluido-dinámico y estructural mediante TCP-IP sockets, intercambiando fuerzas de presión y desplazamientos en los sellos durante la ejecución, y por otra parte, en un innovador esquema de secado-mojado que permite predecir la interacción del agua con los sellos. Se incluyen varios casos de aplicación de la metodología desarrollada sobre el modelo l XR-1B.

  • Perfomance evaluation of the air cushion and seals of a SES in presence of waves and maneuvering in shallow water

     Garcia Espinosa, Julio; Serván Camas, Borja; Di Capua, Daniel; Ubach Fuentes, Pere-Andreu; Oñate Ibáñez de Navarra, Eugenio
    Congress on Numerical Methods in Engineering
    Presentation's date: 2013-06-26
    Presentation of work at congresses

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