The Journal of Strain Analysis for Engineering Design, 2019
The focus of this work is on the computational modeling of a pendulum made of a hyperelastic mate... more The focus of this work is on the computational modeling of a pendulum made of a hyperelastic material and the corresponding experimental validation with the aim of contributing to the study of a material commonly used in seismic absorber devices. From the proposed dynamics experiment, the motion of the pendulum is recorded using a high-speed camera. The evolution of the pendulum’s positions is recovered using a capturing motion technique by tracking markers. The simulation of the problem is developed in the framework of a parallel multi-physics code. Particular emphasis is placed on the analysis of the Newmark integration scheme and the use of Rayleigh damping model. In particular, the time step size effect is analyzed. A strong time step size dependency is obtained for dissipative time integration schemes, while the Rayleigh damping formulation without time integration dissipation shows time step–independent results when convergence is achieved.
Abstract The development of predictive numerical methods, which accurately represent the progress... more Abstract The development of predictive numerical methods, which accurately represent the progressive failure of long fiber composite materials, is nowadays required for the achievement of optimized mechanical responses in terms of load bearing capacities of modern composite structures. In this investigation, two characteristic failure mechanisms of long fiber composites, denominated as intralaminar and translaminar fracture, are simulated by means of a novel version of the phase field (PF) approach of fracture. This numerical strategy encompasses a sort of gradient-enhanced damage formulation rooted in the Griffith theory of fracture, which is herewith extended for its use in composite laminates applications. In order to assess its verification and validation, the predictions obtained using the present formulation are compared against experimental results and two well-established alternative computational methods, which correspond to an anisotropic local-based continuum damage model and a cohesive zone model. The comparisons demonstrate that the PF approach with the proposed formulation provides reliable and robust predictions under quasi-static loading, but with a higher versatility regarding the potential of triggering arbitrarily complex crack paths with intricate topology over alternative techniques.
International journal for numerical methods in biomedical engineering, Jan 16, 2018
In this work we present a fully coupled fluid-electro-mechanical model of a 50th percentile human... more In this work we present a fully coupled fluid-electro-mechanical model of a 50th percentile human heart. The model is implemented on Alya, the BSC multi-physics parallel code, capable of running efficiently in supercomputers. Blood in the cardiac cavities is modelled by the incompressible Navier-Stokes equations and an Arbitrary Lagrangian-Eulerian (ALE) scheme. Electrophysiology is modelled with a monodomain scheme and the O'Hara-Rudy cell model. Solid mechanics is modelled with a total-Lagrangian formulation for discrete strains using the Holzapfel-Ogden cardiac tissue material model. The three problems are simultaneously and bidirectionally coupled through an electro-mechanical feedback and a fluid-structure interaction scheme. In this paper we present the scheme in detail and propose it as a computational cardiac workbench.
Proceedings of the Third International Conference on Parallel, Distributed, Grid and Cloud Computing for Engineering
ABSTRACT This paper introduces an hybrid parallel model of the solid mechanics simulation strateg... more ABSTRACT This paper introduces an hybrid parallel model of the solid mechanics simulation strategy of Alya-High Performance Computational Mechanics, a multi-physics code for supercomputing platforms, developed at Barcelona Supercomputing Center. The goal of the paper is the parallelization strategy, which is chosen as a hybrid MPI/OpenMP model in order to take advantage of all the levels of parallelism that a multicore architecture offers. The paper describes the main features: numerical implementation, algorithms, solution schemes, parallel issues and code engineering. Space and time discretization are based on the finite element method and on finite differences respectively. The solution scheme presented is a total Lagrangian formulation for large deformations, with Newton schemes to cope with non-linearities. Time integration is done either explicitly or implicitly. To exploit the thread-level parallelism of multicore architectures, OpenMP parallelization is introduced in the most time-consuming routines of the solid mechanics, mainly the element assembly and the iterative solver. Additionally, as the communications between threads are via shared memory, there would be a reduction of the communication cost between processors. The main ideas implemented behind the parallel I/O aspects are detailed. Preliminary scalability results are presented for a three-dimensional beam test that requires large data structures. The results obtained are encouraging, outperforming the current MPI-based Alya implementation.
Discontinuous Galerkin methods have emerged in recent years as a reasonable alternative for nonli... more Discontinuous Galerkin methods have emerged in recent years as a reasonable alternative for nonlinear conservation equations. In particular, their inherent structure (the need of a numerical flux based on a suitable approximate Riemann solver which in practice introduces some stabilization) seem to suggest that they are specially adapted to capture shocks. however, the usual numerical fluxes are not sufficient to stabilize the solution in the presence of shocks for high-order discontinuous Galerkin. Thus, slope-limiter methods, which are extensions of finite volume methods, have been proposed for high-order approximations. Here it is shown that these techniques require mesh adaption and a new approach based on the introduction of artificial diffusion into the original equations is presented. The order is not systematically decreased to one in the presence of the shock, large high-order elements can be used, and several linear and nonlinear tests demonstrate the efficiency of the proposed methodology.
The Journal of Strain Analysis for Engineering Design, 2019
The focus of this work is on the computational modeling of a pendulum made of a hyperelastic mate... more The focus of this work is on the computational modeling of a pendulum made of a hyperelastic material and the corresponding experimental validation with the aim of contributing to the study of a material commonly used in seismic absorber devices. From the proposed dynamics experiment, the motion of the pendulum is recorded using a high-speed camera. The evolution of the pendulum’s positions is recovered using a capturing motion technique by tracking markers. The simulation of the problem is developed in the framework of a parallel multi-physics code. Particular emphasis is placed on the analysis of the Newmark integration scheme and the use of Rayleigh damping model. In particular, the time step size effect is analyzed. A strong time step size dependency is obtained for dissipative time integration schemes, while the Rayleigh damping formulation without time integration dissipation shows time step–independent results when convergence is achieved.
Abstract The development of predictive numerical methods, which accurately represent the progress... more Abstract The development of predictive numerical methods, which accurately represent the progressive failure of long fiber composite materials, is nowadays required for the achievement of optimized mechanical responses in terms of load bearing capacities of modern composite structures. In this investigation, two characteristic failure mechanisms of long fiber composites, denominated as intralaminar and translaminar fracture, are simulated by means of a novel version of the phase field (PF) approach of fracture. This numerical strategy encompasses a sort of gradient-enhanced damage formulation rooted in the Griffith theory of fracture, which is herewith extended for its use in composite laminates applications. In order to assess its verification and validation, the predictions obtained using the present formulation are compared against experimental results and two well-established alternative computational methods, which correspond to an anisotropic local-based continuum damage model and a cohesive zone model. The comparisons demonstrate that the PF approach with the proposed formulation provides reliable and robust predictions under quasi-static loading, but with a higher versatility regarding the potential of triggering arbitrarily complex crack paths with intricate topology over alternative techniques.
International journal for numerical methods in biomedical engineering, Jan 16, 2018
In this work we present a fully coupled fluid-electro-mechanical model of a 50th percentile human... more In this work we present a fully coupled fluid-electro-mechanical model of a 50th percentile human heart. The model is implemented on Alya, the BSC multi-physics parallel code, capable of running efficiently in supercomputers. Blood in the cardiac cavities is modelled by the incompressible Navier-Stokes equations and an Arbitrary Lagrangian-Eulerian (ALE) scheme. Electrophysiology is modelled with a monodomain scheme and the O'Hara-Rudy cell model. Solid mechanics is modelled with a total-Lagrangian formulation for discrete strains using the Holzapfel-Ogden cardiac tissue material model. The three problems are simultaneously and bidirectionally coupled through an electro-mechanical feedback and a fluid-structure interaction scheme. In this paper we present the scheme in detail and propose it as a computational cardiac workbench.
Proceedings of the Third International Conference on Parallel, Distributed, Grid and Cloud Computing for Engineering
ABSTRACT This paper introduces an hybrid parallel model of the solid mechanics simulation strateg... more ABSTRACT This paper introduces an hybrid parallel model of the solid mechanics simulation strategy of Alya-High Performance Computational Mechanics, a multi-physics code for supercomputing platforms, developed at Barcelona Supercomputing Center. The goal of the paper is the parallelization strategy, which is chosen as a hybrid MPI/OpenMP model in order to take advantage of all the levels of parallelism that a multicore architecture offers. The paper describes the main features: numerical implementation, algorithms, solution schemes, parallel issues and code engineering. Space and time discretization are based on the finite element method and on finite differences respectively. The solution scheme presented is a total Lagrangian formulation for large deformations, with Newton schemes to cope with non-linearities. Time integration is done either explicitly or implicitly. To exploit the thread-level parallelism of multicore architectures, OpenMP parallelization is introduced in the most time-consuming routines of the solid mechanics, mainly the element assembly and the iterative solver. Additionally, as the communications between threads are via shared memory, there would be a reduction of the communication cost between processors. The main ideas implemented behind the parallel I/O aspects are detailed. Preliminary scalability results are presented for a three-dimensional beam test that requires large data structures. The results obtained are encouraging, outperforming the current MPI-based Alya implementation.
Discontinuous Galerkin methods have emerged in recent years as a reasonable alternative for nonli... more Discontinuous Galerkin methods have emerged in recent years as a reasonable alternative for nonlinear conservation equations. In particular, their inherent structure (the need of a numerical flux based on a suitable approximate Riemann solver which in practice introduces some stabilization) seem to suggest that they are specially adapted to capture shocks. however, the usual numerical fluxes are not sufficient to stabilize the solution in the presence of shocks for high-order discontinuous Galerkin. Thus, slope-limiter methods, which are extensions of finite volume methods, have been proposed for high-order approximations. Here it is shown that these techniques require mesh adaption and a new approach based on the introduction of artificial diffusion into the original equations is presented. The order is not systematically decreased to one in the presence of the shock, large high-order elements can be used, and several linear and nonlinear tests demonstrate the efficiency of the proposed methodology.
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