DSpace Community:
http://hdl.handle.net/2117/427
Fri, 30 Jan 2015 18:55:44 GMT2015-01-30T18:55:44Zwebmaster.bupc@upc.eduUniversitat Politècnica de Catalunya. Servei de Biblioteques i DocumentaciónoA monolithic Lagrangian approach for fluid-structure interaction problems
http://hdl.handle.net/2117/26141
Title: A monolithic Lagrangian approach for fluid-structure interaction problems
Authors: Ryzhakov, Pavel; Rossi, Riccardo; Idelsohn Barg, Sergio Rodolfo; Oñate Ibáñez de Navarra, Eugenio
Abstract: Current work presents a monolithic method for the solution of fluid–structure interaction problems involving flexible structures and free-surface flows. The technique presented is based upon the utilization of a Lagrangian description for both the fluid and the structure. A linear displacement–pressure interpolation pair is used for the fluid whereas the structure utilizes a standard displacement-based formulation. A slight fluid compressibility is assumed that allows to relate the mechanical pressure to the local volume variation. The method described features a global pressure condensation which in turn enables the definition of a purely displacement-based linear system of equations. A matrix-free technique is used for the solution of such linear system, leading to an efficient implementation. The result is a robust method which allows dealing with FSI problems involving arbitrary variations in the shape of the fluid domain. The method is completely free of spurious added-mass effects.Wed, 28 Jan 2015 14:30:47 GMThttp://hdl.handle.net/2117/261412015-01-28T14:30:47ZRyzhakov, Pavel; Rossi, Riccardo; Idelsohn Barg, Sergio Rodolfo; Oñate Ibáñez de Navarra, EugenionoFluid–structure interaction, PFEM, Monolithic FSI, Lagrangian fluids, CFDCurrent work presents a monolithic method for the solution of fluid–structure interaction problems involving flexible structures and free-surface flows. The technique presented is based upon the utilization of a Lagrangian description for both the fluid and the structure. A linear displacement–pressure interpolation pair is used for the fluid whereas the structure utilizes a standard displacement-based formulation. A slight fluid compressibility is assumed that allows to relate the mechanical pressure to the local volume variation. The method described features a global pressure condensation which in turn enables the definition of a purely displacement-based linear system of equations. A matrix-free technique is used for the solution of such linear system, leading to an efficient implementation. The result is a robust method which allows dealing with FSI problems involving arbitrary variations in the shape of the fluid domain. The method is completely free of spurious added-mass effects.On the application of two-fluid flows solver to the casting problem
http://hdl.handle.net/2117/26118
Title: On the application of two-fluid flows solver to the casting problem
Authors: Kamran, Kazem; Rossi, Riccardo; Dadvand, Pooyan; Idelsohn Barg, Sergio Rodolfo
Abstract: 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.Tue, 27 Jan 2015 14:24:07 GMThttp://hdl.handle.net/2117/261182015-01-27T14:24:07ZKamran, Kazem; Rossi, Riccardo; Dadvand, Pooyan; Idelsohn Barg, Sergio RodolfonoThis 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.Optimization method for the determination of material parameters in damaged composite structures
http://hdl.handle.net/2117/25179
Title: Optimization method for the determination of material parameters in damaged composite structures
Authors: Comellas Sanfeliu, Ester; Valdez Peña, Sergio Ivvan; Oller Martínez, Sergio Horacio; Botello, S.
Abstract: An optimization method to identify the material parameters of composite structures using an inverse method is proposed. This methodology compares experimental results with their numerical reproduction using the finite element method in order to obtain an estimation of the error between the results. This error estimation is then used by an evolutionary optimizer to determine, in an iterative process, the value of the material parameters which result in the best numerical fit. The novelty of the method is in the coupling between the simple genetic algorithm and the mixing theory used to numerically reproduce the composite behavior. The methodology proposed has been validated through a simple example which illustrates the exploitability of the method in relation to the modeling of damaged composite structures.Thu, 08 Jan 2015 15:52:03 GMThttp://hdl.handle.net/2117/251792015-01-08T15:52:03ZComellas Sanfeliu, Ester; Valdez Peña, Sergio Ivvan; Oller Martínez, Sergio Horacio; Botello, S.noComposites, Parameter identification, Inverse method, Finite element method, Mixing theory, Genetic algorithm, COMPDESMAT Project, COMP-DES-MAT ProjectAn optimization method to identify the material parameters of composite structures using an inverse method is proposed. This methodology compares experimental results with their numerical reproduction using the finite element method in order to obtain an estimation of the error between the results. This error estimation is then used by an evolutionary optimizer to determine, in an iterative process, the value of the material parameters which result in the best numerical fit. The novelty of the method is in the coupling between the simple genetic algorithm and the mixing theory used to numerically reproduce the composite behavior. The methodology proposed has been validated through a simple example which illustrates the exploitability of the method in relation to the modeling of damaged composite structures.Multi-objective design optimisation of a 3D-rail stamping process using a robust multi-objective optimisation platform (RMOP)
http://hdl.handle.net/2117/25108
Title: Multi-objective design optimisation of a 3D-rail stamping process using a robust multi-objective optimisation platform (RMOP)
Authors: Lee, DongSeop; Coma Company, Martí; Espinoza Román, Héctor Gabriel; Fruitós Bickham, Óscar Alejandro; Pons Prats, Jordi
Abstract: The paper investigates the multi-objective design optimisation of a stamping process to control the final shape and the final quality using advanced high strength steels. The design problem of the stamping process is formulated to minimise the difference between the desired shape and the final geometry obtained by numerical simulation accounting elastic springback.
In addition, the final product quality is maximised by improving safety zones without wrinkling, thinning, or
failure.
Numerical results show that the proposed methodology improves the final product quality while reduces
its springback.Fri, 19 Dec 2014 11:49:34 GMThttp://hdl.handle.net/2117/251082014-12-19T11:49:34ZLee, DongSeop; Coma Company, Martí; Espinoza Román, Héctor Gabriel; Fruitós Bickham, Óscar Alejandro; Pons Prats, JordinoForming process, Robust Multi-Objective Optimization, Genetic Algorithms, Computational plasticityThe paper investigates the multi-objective design optimisation of a stamping process to control the final shape and the final quality using advanced high strength steels. The design problem of the stamping process is formulated to minimise the difference between the desired shape and the final geometry obtained by numerical simulation accounting elastic springback.
In addition, the final product quality is maximised by improving safety zones without wrinkling, thinning, or
failure.
Numerical results show that the proposed methodology improves the final product quality while reduces
its springback.Finite element computation of diphthong sounds using tuned two-dimensional vocal tracts
http://hdl.handle.net/2117/24984
Title: Finite element computation of diphthong sounds using tuned two-dimensional vocal tracts
Authors: Arnela, Marc; Guasch Fortuny, Oriol; Codina, Ramon; Espinoza Román, Héctor Gabriel
Abstract: Finite element methods (FEM) are increasingly being used to simulate the acoustics of the vocal tract. For vowel production, the irreducible wave equation for the acoustic pressure is typically solved. However, diphthong sounds require moving vocal tract geometries so that the wave equation has to be expressed in an Arbitrary Lagrangian-Eulerian (ALE) framework. It then becomes more convenient to directly work with the wave equation in its mixed form, which not only involves the acoustic pressure but also the acoustic velocity. In turn, this entails some numerical difficulties that require resorting to stabilized FEM approaches. In this work, FEM simulations for the wave equation in
mixed form are carried out to produce some diphthongs. Tuned two-dimensional vocal tracts are used which mimic the behavior of three-dimensional vocal tracts with circular cross-section.Wed, 10 Dec 2014 14:39:14 GMThttp://hdl.handle.net/2117/249842014-12-10T14:39:14ZArnela, Marc; Guasch Fortuny, Oriol; Codina, Ramon; Espinoza Román, Héctor GabrielnoFinite element methods (FEM) are increasingly being used to simulate the acoustics of the vocal tract. For vowel production, the irreducible wave equation for the acoustic pressure is typically solved. However, diphthong sounds require moving vocal tract geometries so that the wave equation has to be expressed in an Arbitrary Lagrangian-Eulerian (ALE) framework. It then becomes more convenient to directly work with the wave equation in its mixed form, which not only involves the acoustic pressure but also the acoustic velocity. In turn, this entails some numerical difficulties that require resorting to stabilized FEM approaches. In this work, FEM simulations for the wave equation in
mixed form are carried out to produce some diphthongs. Tuned two-dimensional vocal tracts are used which mimic the behavior of three-dimensional vocal tracts with circular cross-section.Strain localization and failure mechanics for elastoplastic damage solids
http://hdl.handle.net/2117/24663
Title: Strain localization and failure mechanics for elastoplastic damage solids
Authors: Wu, Jian-Ying; Cervera Ruiz, Miguel
Abstract: This work investigates systematically strain localization and failure mechanics for elastoplastic damage solids. Two complementary methodologies, i.e., traction-based discontinuities localized in an elastic solid and strain localization of a stress-based inelastic softening solid, are addressed. In the former it is assumed a priori that the discontinuity (band) forms with a continuous stress field and along the known orientation. A traction-based failure criterion is introduced to characterize the discontinuity (band) and the orientation is determined from Mohr’s maximization postulate. If the (apparent) displacement jumps are retained as independent variables, the strong/regularized
discontinuity approaches follow, requiring constitutive models for both the bulk and discontinuity (band). Elimination of the displacement jumps at the material point level results in the embedded/smeared discontinuity approaches in which an overall inelastic constitutive model fulfilling the static constraint suffices. The second methodology is then adopted to check whether the assumed strain localization can occur and identify its consequences on the resulting approaches. The kinematic constraint guaranteeing stress boundedness/continuity upon strain localization is established for general inelastic softening solids. Application to a unified elastoplastic damage model naturally yields all the ingredients of a localized model for the discontinuity (band), justifying the first methodology. Two dual but not necessarily equivalent approaches, i.e., the traction-based elastoplastic damage model and the stress-based projected discontinuity model, are identified. The former is equivalent to the embedded/smeared discontinuity approaches, whereas in the later the discontinuity orientation and associated failure criterion, not given a priori, are determined consistently from the kinematic constraint. The bi-directional connections and equivalence conditions between the
traction- and stress-based approaches are classified. Closed-form 2D results under plane stress condition are also given, with the classical Rankine, Mohr-Coulomb, von Mises and Drucker-Prager criteria analyzed as the illustrative examples. A generic failure criterion of either elliptic, parabolic or hyperbolic type, is then considered in a unified manner, resulting in many failure criteria frequently employed in practice.Mon, 10 Nov 2014 19:41:30 GMThttp://hdl.handle.net/2117/246632014-11-10T19:41:30ZWu, Jian-Ying; Cervera Ruiz, MiguelnoStrain localization, localized failure, constitutive behavior, discontinuities, fracture, plasticity, damageThis work investigates systematically strain localization and failure mechanics for elastoplastic damage solids. Two complementary methodologies, i.e., traction-based discontinuities localized in an elastic solid and strain localization of a stress-based inelastic softening solid, are addressed. In the former it is assumed a priori that the discontinuity (band) forms with a continuous stress field and along the known orientation. A traction-based failure criterion is introduced to characterize the discontinuity (band) and the orientation is determined from Mohr’s maximization postulate. If the (apparent) displacement jumps are retained as independent variables, the strong/regularized
discontinuity approaches follow, requiring constitutive models for both the bulk and discontinuity (band). Elimination of the displacement jumps at the material point level results in the embedded/smeared discontinuity approaches in which an overall inelastic constitutive model fulfilling the static constraint suffices. The second methodology is then adopted to check whether the assumed strain localization can occur and identify its consequences on the resulting approaches. The kinematic constraint guaranteeing stress boundedness/continuity upon strain localization is established for general inelastic softening solids. Application to a unified elastoplastic damage model naturally yields all the ingredients of a localized model for the discontinuity (band), justifying the first methodology. Two dual but not necessarily equivalent approaches, i.e., the traction-based elastoplastic damage model and the stress-based projected discontinuity model, are identified. The former is equivalent to the embedded/smeared discontinuity approaches, whereas in the later the discontinuity orientation and associated failure criterion, not given a priori, are determined consistently from the kinematic constraint. The bi-directional connections and equivalence conditions between the
traction- and stress-based approaches are classified. Closed-form 2D results under plane stress condition are also given, with the classical Rankine, Mohr-Coulomb, von Mises and Drucker-Prager criteria analyzed as the illustrative examples. A generic failure criterion of either elliptic, parabolic or hyperbolic type, is then considered in a unified manner, resulting in many failure criteria frequently employed in practice.Finite element modeling of delamination in advanced composite beams and plates using one and two dimensional finite elements based on the refined zigzag theory
http://hdl.handle.net/2117/24662
Title: Finite element modeling of delamination in advanced composite beams and plates using one and two dimensional finite elements based on the refined zigzag theory
Authors: Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martínez, Sergio HoracioMon, 10 Nov 2014 19:31:57 GMThttp://hdl.handle.net/2117/246622014-11-10T19:31:57ZEijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martínez, Sergio HoracionoRobust volume mesh generation for non-watertight geometries
http://hdl.handle.net/2117/24661
Title: Robust volume mesh generation for non-watertight geometries
Authors: Coll Sans, Abel; Oñate Ibáñez de Navarra, Eugenio; Dadvand, Pooyan
Abstract: Nowadays large part of the time needed to perform a numerical simulation is spent in preprocessing, especially in the geometry cleaning operations and mesh generation. Furthermore, these operations are not easy to automatize because they depend strongly on each geometrical model and they often need human interaction. Many of these operations are needed to obtain a watertight geometry. Even with a clean geometry, classical unstructured meshing methods (like Delaunay or Advancing Front based ones) present critical weak points like the need of a given quality in the boundary mesh or a relatively smooth size transition. These aspects decrease their robustness and imply an extra effort in order to reach the final mesh. Octree based meshers try to relax some of these requirements. In the present work an octree based mesher for unstructured tetrahedra is presented. The proposed mesher ensures the mesh generation avoiding most of the geometry cleaning operations. It is based in the following steps: fit an octree onto the model, refine it following given criteria, apply a tetrahedra pattern to the octree cells and adapt the tetrahedra close to the contours in order to represent accurately the boundary shape. An important and innovative aspect of the proposed algorithm is it ensures the final mesh preserves the topology and the
geometric features of the original model. The method uses a Ray Casting based algorithm for the identification of the inner and outer parts of the volumes involved in the model. This technique allows the
mesh generation of volumes even with non-watertight boundaries, and also opens the use of the mesher for immersed methods only applying slight modifications to the algorithm. The main advantages of the presented mesher are: robustness, no need for watertight
boundaries, independent on the contour mesh quality, preservation of geometrical features (corners and ridges), original geometric topology guaranteed, accurate representation of the contours, valid for immersed methods, and fast performance. A lot of time in the preprocessing part of the numerical simulation is saved thanks to the robustness of the mesher, which allows skipping most of the geometry cleaning operations. A shared memory parallel implementation of the algorithm has been done. The effectiveness of the algorithm and its implementation has been verified by some validation examples.Mon, 10 Nov 2014 19:21:48 GMThttp://hdl.handle.net/2117/246612014-11-10T19:21:48ZColl Sans, Abel; Oñate Ibáñez de Navarra, Eugenio; Dadvand, PooyannoNowadays large part of the time needed to perform a numerical simulation is spent in preprocessing, especially in the geometry cleaning operations and mesh generation. Furthermore, these operations are not easy to automatize because they depend strongly on each geometrical model and they often need human interaction. Many of these operations are needed to obtain a watertight geometry. Even with a clean geometry, classical unstructured meshing methods (like Delaunay or Advancing Front based ones) present critical weak points like the need of a given quality in the boundary mesh or a relatively smooth size transition. These aspects decrease their robustness and imply an extra effort in order to reach the final mesh. Octree based meshers try to relax some of these requirements. In the present work an octree based mesher for unstructured tetrahedra is presented. The proposed mesher ensures the mesh generation avoiding most of the geometry cleaning operations. It is based in the following steps: fit an octree onto the model, refine it following given criteria, apply a tetrahedra pattern to the octree cells and adapt the tetrahedra close to the contours in order to represent accurately the boundary shape. An important and innovative aspect of the proposed algorithm is it ensures the final mesh preserves the topology and the
geometric features of the original model. The method uses a Ray Casting based algorithm for the identification of the inner and outer parts of the volumes involved in the model. This technique allows the
mesh generation of volumes even with non-watertight boundaries, and also opens the use of the mesher for immersed methods only applying slight modifications to the algorithm. The main advantages of the presented mesher are: robustness, no need for watertight
boundaries, independent on the contour mesh quality, preservation of geometrical features (corners and ridges), original geometric topology guaranteed, accurate representation of the contours, valid for immersed methods, and fast performance. A lot of time in the preprocessing part of the numerical simulation is saved thanks to the robustness of the mesher, which allows skipping most of the geometry cleaning operations. A shared memory parallel implementation of the algorithm has been done. The effectiveness of the algorithm and its implementation has been verified by some validation examples.Computational model of the human urinary blader
http://hdl.handle.net/2117/24659
Title: Computational model of the human urinary blader
Authors: Monteiro, Virginia; Oñate Ibáñez de Navarra, Eugenio; Oller Martínez, Sergio Horacio
Abstract: 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.Mon, 10 Nov 2014 19:12:21 GMThttp://hdl.handle.net/2117/246592014-11-10T19:12:21ZMonteiro, Virginia; Oñate Ibáñez de Navarra, Eugenio; Oller Martínez, Sergio HoracionoThe 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
http://hdl.handle.net/2117/24658
Title: A compressible Lagrangian framework for the simulation of underwater implosion problems
Authors: Kamran, Kazem; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Rossi, Riccardo
Abstract: 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. A nodally perfect matched definition of the interface is used 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.Mon, 10 Nov 2014 18:59:40 GMThttp://hdl.handle.net/2117/246582014-11-10T18:59:40ZKamran, Kazem; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Rossi, RiccardonoThe 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. A nodally perfect matched definition of the interface is used 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.A finite point method for adaptive-three-dimensional compressible flow calculations
http://hdl.handle.net/2117/24488
Title: A finite point method for adaptive-three-dimensional compressible flow calculations
Authors: Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo
Abstract: The finite point method (FPM) is a meshless technique, which is based on both, a weighted least-squares numerical approximation on local clouds of points and a collocation technique which allows obtaining the discrete system of equations. The research work we present is part of a broader investigation into the capabilities of the FPM to deal with 3D applications concerning real compressible fluid flow problems. In the first part of this work, the upwind-biased scheme employed for solving the flow equations is described. Secondly, with the aim of exploiting the meshless capabilities, an h-adaptive methodology for 2D and 3D compressible flow calculations is developed. This adaptive technique applies a solution-based indicator in order to identify local clouds where new points should be inserted in or existing points could be safely removed from the computational domain. The flow solver and the adaptive procedure have been evaluated and the results are encouraging. Several numerical examples are provided in order to illustrate the good performance of the numerical methods presented.
Description: Electronic version of an article published as "International journal for numerical methods in fluids", vol. 60, no 9, 2009, p. 937-971. DOI:10.1002/fld.1892 <http://onlinelibrary.wiley.com/doi/10.1002/fld.1892/abstract>Mon, 27 Oct 2014 15:18:46 GMThttp://hdl.handle.net/2117/244882014-10-27T15:18:46ZOrtega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio RodolfonoMeshless methods, Finite point method, Adaptivity, Collocation, Compressible flow, Time integration explicitThe finite point method (FPM) is a meshless technique, which is based on both, a weighted least-squares numerical approximation on local clouds of points and a collocation technique which allows obtaining the discrete system of equations. The research work we present is part of a broader investigation into the capabilities of the FPM to deal with 3D applications concerning real compressible fluid flow problems. In the first part of this work, the upwind-biased scheme employed for solving the flow equations is described. Secondly, with the aim of exploiting the meshless capabilities, an h-adaptive methodology for 2D and 3D compressible flow calculations is developed. This adaptive technique applies a solution-based indicator in order to identify local clouds where new points should be inserted in or existing points could be safely removed from the computational domain. The flow solver and the adaptive procedure have been evaluated and the results are encouraging. Several numerical examples are provided in order to illustrate the good performance of the numerical methods presented.Comparing a sumulated loss scenario with the observed earthquake damage: the Lorca 2011 case study
http://hdl.handle.net/2117/24085
Title: Comparing a sumulated loss scenario with the observed earthquake damage: the Lorca 2011 case study
Authors: Salgado Galvez, Mario A.; Carreño Tibaduiza, Martha Liliana; Barbat Barbat, Horia Alejandro; Cardona Arboleda, Omar Dario
Abstract: A loss assessment was performed for the buildings of Lorca, Spain, considering an earthquake hazard scenario with similar characteristics to those of a real event which occurred on May 11th 2011, in terms of epicentre, depth and magnitude. This low-to moderate earthquake caused severe damage and disruption in the region and especially on the city. A building by building resolution database was developed and used for damage and loss assessment. The portfolio of buildings was characterized by means of relevant indexes capturing information from a structural point of view such as age, main construction materials, number of stories, and building class. A replacement cost approach was
selected for the analysis in order to calculate the direct losses incurred by the event. Hazard and vulnerability were modeled in a probabilistic way, considering their inherent uncertainties which were also taken into account in the damage and loss calculation process. Losses have been expressed in terms of the mean damage ratio of each dwelling and since the analysis has been performed on a geographical information system platform, the distribution of the damage and its categories was mapped for the entire urban centre. The simulated damage was compared with the observed damage reported by the local authorities that inspected the city after the event.Wed, 17 Sep 2014 14:21:01 GMThttp://hdl.handle.net/2117/240852014-09-17T14:21:01ZSalgado Galvez, Mario A.; Carreño Tibaduiza, Martha Liliana; Barbat Barbat, Horia Alejandro; Cardona Arboleda, Omar DarionoA loss assessment was performed for the buildings of Lorca, Spain, considering an earthquake hazard scenario with similar characteristics to those of a real event which occurred on May 11th 2011, in terms of epicentre, depth and magnitude. This low-to moderate earthquake caused severe damage and disruption in the region and especially on the city. A building by building resolution database was developed and used for damage and loss assessment. The portfolio of buildings was characterized by means of relevant indexes capturing information from a structural point of view such as age, main construction materials, number of stories, and building class. A replacement cost approach was
selected for the analysis in order to calculate the direct losses incurred by the event. Hazard and vulnerability were modeled in a probabilistic way, considering their inherent uncertainties which were also taken into account in the damage and loss calculation process. Losses have been expressed in terms of the mean damage ratio of each dwelling and since the analysis has been performed on a geographical information system platform, the distribution of the damage and its categories was mapped for the entire urban centre. The simulated damage was compared with the observed damage reported by the local authorities that inspected the city after the event.Probabilistic earthquake risk assessment of Barcelona using CAPRA
http://hdl.handle.net/2117/24084
Title: Probabilistic earthquake risk assessment of Barcelona using CAPRA
Authors: Marulanda Fraume, Mabel Cristina; Carreño Tibaduiza, Martha Liliana; Cardona Arboleda, Omar Dario; Ordaz Schroeder, Mario Gustavo; Barbat Barbat, Horia Alejandro
Abstract: The seismic risk assessment of Barcelona has been performed using the modules of CAPRA and the corresponding holistic estimation of the seismic risk of this urban area. In addition, according to the physical risk results and the information on the socio-economic indicators of the city, was performed a holistic evaluation of seismic risk, which is a valuable result to facilitate the integrated risk management by the different stakeholders involved in risk reduction decision making.Wed, 17 Sep 2014 14:16:18 GMThttp://hdl.handle.net/2117/240842014-09-17T14:16:18ZMarulanda Fraume, Mabel Cristina; Carreño Tibaduiza, Martha Liliana; Cardona Arboleda, Omar Dario; Ordaz Schroeder, Mario Gustavo; Barbat Barbat, Horia AlejandronoThe seismic risk assessment of Barcelona has been performed using the modules of CAPRA and the corresponding holistic estimation of the seismic risk of this urban area. In addition, according to the physical risk results and the information on the socio-economic indicators of the city, was performed a holistic evaluation of seismic risk, which is a valuable result to facilitate the integrated risk management by the different stakeholders involved in risk reduction decision making.Holistic seismic risk assessment of port of Spain: an integrated evaluation and tool in the framework of CAPRA
http://hdl.handle.net/2117/24083
Title: Holistic seismic risk assessment of port of Spain: an integrated evaluation and tool in the framework of CAPRA
Authors: Carreño Tibaduiza, Martha Liliana; Cardona Arboleda, Omar Dario; Barbat Barbat, Horia Alejandro; Velasquez, Cesar A.; Salgado Galvez, Mario A.
Abstract: In recent years disaster risk has been defined, for management purposes, as the potential economic, social and environmental consequences of hazardous events that may occur in a given period of time. However, in many cases, the concept of risk has been defined in a fragmentary way according to each scientific discipline involved in its estimation. In order to evaluate risk according to the above stated definition, a multidisciplinary evaluation is necessary. This evaluation should take into account not only the expected physical damage, the number and type of casualties or economic losses, but also the conditions related to social fragility and lack of resilience which favour the second order effects when a hazardous event strikes an urban centre.Wed, 17 Sep 2014 14:12:33 GMThttp://hdl.handle.net/2117/240832014-09-17T14:12:33ZCarreño Tibaduiza, Martha Liliana; Cardona Arboleda, Omar Dario; Barbat Barbat, Horia Alejandro; Velasquez, Cesar A.; Salgado Galvez, Mario A.noIn recent years disaster risk has been defined, for management purposes, as the potential economic, social and environmental consequences of hazardous events that may occur in a given period of time. However, in many cases, the concept of risk has been defined in a fragmentary way according to each scientific discipline involved in its estimation. In order to evaluate risk according to the above stated definition, a multidisciplinary evaluation is necessary. This evaluation should take into account not only the expected physical damage, the number and type of casualties or economic losses, but also the conditions related to social fragility and lack of resilience which favour the second order effects when a hazardous event strikes an urban centre.Hybrid loss assessment curve for Colombia: a prospective and a retrospective approach
http://hdl.handle.net/2117/24082
Title: Hybrid loss assessment curve for Colombia: a prospective and a retrospective approach
Authors: Velasquez, Cesar A.; Cardona Arboleda, Omar Dario; Mora Cuevas, Miguel; Yamín Lacouture, Luis Eduardo; Carreño Tibaduiza, Martha Liliana; Barbat Barbat, Horia Alejandro
Abstract: Countries prone to seismic hazard need to assess the expected risk as a permanent activity in their financial plan; otherwise, they will experience a lack in the information required for the application of disaster risk reduction policies. In this article, a risk assessment methodology is proposed that uses, on the one hand, empiric estimations of loss, based on information available in local disaster data bases, allowing to estimate losses due to small events; on the other hand, it uses probabilistic evaluations to estimate loss for greater or even catastrophic events for which information is not available due the lack of historical data. A “hybrid” loss exceedance curve, which represents the disaster risk in a proper and complete way, is thus determined. This curve merges two components: the
corresponding to small and moderate losses, calculated by using an inductive and retrospective analysis, and the corresponding to extreme losses, calculated by using a deductive and prospective analysis.Wed, 17 Sep 2014 14:02:55 GMThttp://hdl.handle.net/2117/240822014-09-17T14:02:55ZVelasquez, Cesar A.; Cardona Arboleda, Omar Dario; Mora Cuevas, Miguel; Yamín Lacouture, Luis Eduardo; Carreño Tibaduiza, Martha Liliana; Barbat Barbat, Horia AlejandronoCountries prone to seismic hazard need to assess the expected risk as a permanent activity in their financial plan; otherwise, they will experience a lack in the information required for the application of disaster risk reduction policies. In this article, a risk assessment methodology is proposed that uses, on the one hand, empiric estimations of loss, based on information available in local disaster data bases, allowing to estimate losses due to small events; on the other hand, it uses probabilistic evaluations to estimate loss for greater or even catastrophic events for which information is not available due the lack of historical data. A “hybrid” loss exceedance curve, which represents the disaster risk in a proper and complete way, is thus determined. This curve merges two components: the
corresponding to small and moderate losses, calculated by using an inductive and retrospective analysis, and the corresponding to extreme losses, calculated by using a deductive and prospective analysis.