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Papers by Guillaume Houzeaux

Lecture Notes in Computational Science and Engineering, 2008

We present in this paper the experience of the authors in solving very large problems of computat... more We present in this paper the experience of the authors in solving very large problems of computational mechanics on a supercomputer. The authors are researchers of the Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS), a brand new research center in Spain, which hosts the fastest supercomputer in Europe and the fifth in the world: MareNostrum (TOP500, November 2006). A brief

Lecture Notes in Computational Science and Engineering, 2013

The Open Waste Management Journal, 2010

Lecture Notes in Computational Science and Engineering, 2010

49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2011

ABSTRACT

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 2010

: This work presents a geometrical domain decomposition (DD) strategy for the finite element solu... more : This work presents a geometrical domain decomposition (DD) strategy for the finite element solution of incompressible fluid problems involving moving subregions. The DD algorithm is based on the iterative update of the boundary conditions on the interfaces between the subregions, known as iteration-by-subdomain method. Some subregions may be in relative motion. Therefore, in order to treat the constant change of the interfaces configuration, an embedding technique is used together with a Dirichlet/Neumann method. This method enables to couple di#erent flow regions, each one running on separate processes, without major alteration of the original fluid code. The coupling is performed by a master program which coordinates the processes and passes the data back and forth to the slaves. In the first section, the governing equations of the fluid solver are introduced. The following section presents theoretical as well as implementation aspects of the DD algorithm. Finally, the last sect...

Imaging techniques for geophysic prospection of sea bottom are extremely demanding in terms of ma... more Imaging techniques for geophysic prospection of sea bottom are extremely demanding in terms of mathematical methods and computational resources (8). This is because the measurements are going deeper than before, thus making the structures identification a hard task, a nd the datasets to be com- puted huge. Besides, the current trend is to analyze the images in three dimensions (3D) (4), adding an extra difficulty to the process. Currently, the prospection process is h ighly automatized by computer programs, where these programs not only implement and solve the mathematical model, but also carry the burden of the datasets manipulation, particularly in pre and post proces sing. All of these demands (complex mathematical models to be solved and huge datasets to be manipulated) lead us to high per- formance computing (HPC) environments, which are mainly available by supercomputers composed by thousands of computational nodes, thus efficient parallelization of those c omputer programs is...

2012 SC Companion: High Performance Computing, Networking Storage and Analysis, 2012

ABSTRACT Flows with moving interfaces appear in a wide range of real world problems. This report,... more ABSTRACT Flows with moving interfaces appear in a wide range of real world problems. This report, accompanying the video Two fluids level set: High performance simulation and post processing" presents the implementation of a Level Set method for two fluid flows in the parallel finite element code Alya that can scale up to thousands of processors. To give an idea of the versatility of the implementation examples extending from the flushing of a toilet to the simulation of free surface flows around ship hulls are presented. The spatial discretization is based on unstructured linear finite elements, tetrahedras and prisms that allow a great degree of flexibility for complex geometries as will be shown in the examples. The time discretization uses a standard trapezoidal rule. The position of the moving interface is captured with the Level Set technique that is better suited for complex flows than interface tracking schemes. The jump in the fluid properties is smoothed in a region close to the interface. For ship hydrodynamics simulations the model has been coupled with the SST k-ω turbulence model.

Journal of the Royal Society, Interface / the Royal Society, Jan 6, 2015

During a rapid inhalation, such as a sniff, the flow in the airways accelerates and decays quickl... more During a rapid inhalation, such as a sniff, the flow in the airways accelerates and decays quickly. The consequences for flow development and convective transport of an inhaled gas were investigated in a subject geometry extending from the nose to the bronchi. The progress of flow transition and the advance of an inhaled non-absorbed gas were determined using highly resolved simulations of a sniff 0.5 s long, 1 l s⁻¹ peak flow, 364 ml inhaled volume. In the nose, the distribution of airflow evolved through three phases: (i) an initial transient of about 50 ms, roughly the filling time for a nasal volume, (ii) quasi-equilibrium over the majority of the inhalation, and (iii) a terminating phase. Flow transition commenced in the supraglottic region within 20 ms, resulting in large-amplitude fluctuations persisting throughout the inhalation; in the nose, fluctuations that arose nearer peak flow were of much reduced intensity and diminished in the flow decay phase. Measures of gas concen...

Archives of Computational Methods in Engineering, 2014

ABSTRACT While solid mechanics codes are now conventional tools both in industry and research, th... more ABSTRACT While solid mechanics codes are now conventional tools both in industry and research, the increasingly more exigent requirements of both sectors are fuelling the need for more computational power and more advanced algorithms. For obvious reasons, commercial codes are lagging behind academic codes often dedicated either to the implementation of one new technique, or the upscaling of current conventional codes to tackle massively large scale computational problems. Only in a few cases, both approaches have been followed simultaneously. In this article, a solid mechanics simulation strategy for parallel supercomputers based on a hybrid approach is presented. Hybrid parallelization exploits the thread-level parallelism of multicore architectures, combining MPI tasks with OpenMP threads. This paper describes the proposed strategy, programmed in Alya, a parallel multi-physics code. Hybrid parallelization is specially well suited for the current trend of supercomputers, namely large clusters of multicores. The strategy is assessed through transient non-linear solid mechanics problems, both for explicit and implicit schemes, running on thousands of cores. In order to demonstrate the flexibility of the proposed strategy under advance algorithmic evolution of computational mechanics, a non-local parallel overset meshes method (Chimera-like) is implemented and the conservation of the scalability is demonstrated.

Journal of NeuroInterventional Surgery, 2014