6 results on '"Houzeaux, Guillaume"'
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2. A Chimera method based on a Dirichlet/Neumann(Robin) coupling for the Navier–Stokes equations
- Author
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Houzeaux, Guillaume and Codina, Ramon
- Subjects
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FLOWS (Differentiable dynamical systems) , *FINITE element method , *COUPLINGS (Gearing) - Abstract
We present a Chimera method for the numerical solution of incompressible flows past objects in relative motion. The Chimera method is implemented as an iteration-by-subdomain method based on Dirichlet/Neumann(Robin) coupling. The DD method we propose is not only geometric but also algorithmic, for the solution on each subdomain is obtained on separate processes and the exchange of information between the subdomains is carried out by a master code. This strategy is very flexible as it requires almost no modification to the original numerical code. Therefore, only the master code has to be adapted to the numerical codes and the strategies used on each subdomain. As a basic flow solver, we a use stabilized finite element method. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
- View/download PDF
3. Local preconditioning and variational multiscale stabilization for Euler compressible steady flow.
- Author
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Moragues Ginard, Margarida, Vázquez, Mariano, and Houzeaux, Guillaume
- Subjects
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STABILITY (Mechanics) , *EULER equations , *STEADY-state flow , *COMPRESSIBLE flow , *FINITE element method , *STIFFNESS (Mechanics) , *MACH number - Abstract
This paper introduces a preconditioned variational multiscale stabilization (P-VMS) method for compressible flows. In this introductory paper we focus on inviscid flow and steady state problems. The Euler equations are solved on fully unstructured grids and discretized using the finite element method. The P-VMS method can be decomposed into three parts. First, a local preconditioner is applied to the continuous equations to reduce the stiffness while covering a wide range of Mach numbers. Then, the resulting preconditioned system is discretized in space using finite elements and stabilized with a variational multiscale stabilization method adapted for the preconditioned equations. In this paper, the solution is advanced in time using a fully explicit time discretization, although P-VMS is general and can be applied to fully implicit solvers. The proposed method is assessed by comparing convergence and accuracy of the solutions between the non-preconditioned and preconditioned cases, in particular for van Leer–Lee–Roe ’s (1991) and Choi-Merkle ’s (1993) preconditioners, in some selected examples covering a large range of Mach numbers. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
4. Real-space density functional theory and time dependent density functional theory using finite/infinite element methods
- Author
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Soba, Alejandro, Bea, Edgar Alejandro, Houzeaux, Guillaume, Calmet, Hadrien, and Cela, José María
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DENSITY functionals , *FINITE element method , *NUMERICAL analysis , *ELECTRONIC structure , *HARTREE-Fock approximation , *PARALLEL computers , *POLYNOMIALS , *MATHEMATICAL models - Abstract
Abstract: We present a numerical approach using the finite element method to discretize the equations that allow getting a first-principles description of multi-electronic systems within DFT and TD-DFT formalisms. A strictly local polynomial function basis set is used in order to represent the entire real-space domain. Infinite elements are introduced to model the infinite external boundaries in the case of Hartree’s equation. The diagonal mass matrix is obtained using a close integration rule, reducing the generalized eigenvalue problem to a standard one. This framework of electronic structure calculation is embedded in a high performance computing environment with a very good parallel behavior. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
5. On the extension of the integral length-scale approximation model to complex geometries.
- Author
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Lehmkuhl, Oriol, Piomelli, Ugo, and Houzeaux, Guillaume
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MOMENTUM transfer , *EDDY viscosity , *FLOW separation , *GEOMETRIC modeling , *FINITE element method , *MODELS & modelmaking - Abstract
• The Integral Length Scale Approximation Subfilter Scale Model is applied to separated flows. • A procedure to determine the model constant is proposed. • A low-dissipation finite-element method is used. • The model accounts for interactions between numerical error and turbulence modelling errors. • Flows over a sphere and an Ahmed body are computed, and good agreement with the data is obtained. A new model for the unresolved stresses in large-eddy simulations was recently proposed by Piomelli et al. [J Fluid Mech 2015; 766:499–527] and Rouhi et al., [Phys Rev Fluids 2016; 1(4):0444011], in which the length scale is not related to the grid size, but determined based on turbulence properties. This model, the Integral Length-Scale Approximation (ILSA), has a single parameter, s τ , which represents the contribution of the unresolved scales to the momentum transport, and is assigned by the user. We test ILSA in complex geometries using a low-dissipation finite-element method, and propose a rational method to determine s τ on the basis of a grid-convergence study. The interaction of the model with the numerical method and grid topology is studied first; then, two cases are considered: the subcritical flow around a sphere, and the flow over the Ahmed body, a simplified car model. In each case calculations are performed using three grids and varying s τ. With a consistent combination of grid size and s τ the statistical results are in very good agreement with DNS data and experimental measurements. The eddy viscosity is insensitive to sudden variation of the mesh size, and the model adjusts to the different dissipation and diffusion characteristics associated with different grid topologies and numerical techniques. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
6. An XFEM/CZM implementation for massively parallel simulations of composites fracture.
- Author
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Vigueras, Guillermo, Sket, Federico, Samaniego, Cristóbal, Wu, Ling, Noels, Ludovic, Tjahjanto, Denny, Casoni, Eva, Houzeaux, Guillaume, Makradi, Ahmed, Molina-Aldareguia, Jon M., Vázquez, Mariano, and Jérusalem, Antoine
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COMPOSITE materials , *FRACTURE mechanics , *SURFACE cracks , *FINITE element method , *MECHANICAL behavior of materials , *STRENGTH of materials - Abstract
Because of their widely generalized use in many industries, composites are the subject of many research campaigns. More particularly, the development of both accurate and flexible numerical models able to capture their intrinsically multiscale modes of failure is still a challenge. The standard finite element method typically requires intensive remeshing to adequately capture the geometry of the cracks and high accuracy is thus often sacrificed in favor of scalability, and vice versa. In an effort to preserve both properties, we present here an extended finite element method (XFEM) for large scale composite fracture simulations. In this formulation, the standard FEM formulation is partially enriched by use of shifted Heaviside functions with special attention paid to the scalability of the scheme. This enrichment technique offers several benefits since the interpolation property of the standard shape function still holds at the nodes. Those benefits include (i) no extra boundary condition for the enrichment degree of freedom, and (ii) no need for transition/blending regions; both of which contribute to maintaining the scalability of the code. Two different cohesive zone models (CZM) are then adopted to capture the physics of the crack propagation mechanisms. At the intralaminar level, an extrinsic CZM embedded in the XFEM formulation is used. At the interlaminar level, an intrinsic CZM is adopted for predicting the failure. The overall framework is implemented in ALYA, a mechanics code specifically developed for large scale, massively parallel simulations of coupled multi-physics problems. The implementation of both intrinsic and extrinsic CZM models within the code is such that it conserves the extremely efficient scalability of ALYA while providing accurate physical simulations of computationally expensive phenomena. The strong scalability provided by the proposed implementation is demonstrated. The model is ultimately validated against a full experimental campaign of loading tests and X-ray tomography analyzes. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
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