Gauthier WissocqUniversity of Zurich | UZH · Institut für Mathematik
Gauthier Wissocq
PhD
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28
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Introduction
Skills and Expertise
Publications
Publications (28)
The present study focuses on the unphysical effects induced by the use of non-uniform grids in the lattice Boltzmann method. In particular, the convection of vortical structures across a grid refinement interface is likely to generate spurious noise that may impact the whole computation domain. This issue becomes critical in the case of aeroacousti...
An original spectral study of the compressible hybrid lattice Boltzmann method (HLBM) on standard lattice is proposed. In this framework, the mass and momentum equations are addressed using the lattice Boltzmann method (LBM), while finite difference (FD) schemes solve an energy equation. Both systems are coupled with each other thanks to an ideal g...
The discrete velocity Boltzmann equations (DVBE) underlie the attainable properties of all numerical lattice Boltzmann methods (LBM). To that regard, a thorough understanding of their intrinsic hydrodynamic limits and stability properties is mandatory. To achieve this, we propose an analytical study of the eigenvalues obtained by a von Neumann pert...
With the aim of better understanding the numerical properties of the lattice Boltzmann method (LBM), a general methodology is proposed to derive its hydrodynamic limits in the discrete setting. It relies on a Taylor expansion in the limit of low Knudsen numbers. With a single asymptotic analysis, two kinds of deviations with the Navier-Stokes (NS)...
A general methodology is introduced to build conservative numerical models for fluid simulations based on segregated schemes, where mass, momentum and energy equations are solved by different methods. It is here especially designed for developing new numerical discretizations of the total energy equation, adapted to a thermal coupling with the latt...
With the aim of better understanding the numerical properties of the lattice Boltzmann method (LBM), a general methodology is proposed to derive its hydrodynamic limits in the discrete setting. It relies on a Taylor expansion in the limit of low Knudsen numbers. With a single asymptotic analysis, two kinds of deviations with the Navier-Stokes (NS)...
The present study proposes an accurate lattice Boltzmann direct coupling algorithm, well suited for industrial purposes, making it highly valuable for aeroacoustic applications. It is indeed known that the convection of vortical structures across a grid refinement interface, where cell size is abruptly doubled, is likely to generate spurious noise...
An original spectral study of the compressible hybrid lattice Boltzmann method (HLBM) on standard lattice is proposed. In this framework, the mass and momentum equations are addressed using the lattice Boltzmann method (LBM), while finite difference (FD) schemes solve an energy equation. Both systems are coupled with each other thanks to an ideal g...
A unified expression for high-speed compressible segregated consistent lattice Boltzmann methods, namely pressure-based and improved density-based methods, is given. It is theoretically proved that in the absence of forcing terms these approaches are strictly identical and can be recast in a unique form. An important result is that the difference w...
The present work proposes a general methodology to study stability and isotropy properties of lattice Boltzmann (LB) schemes. As a first investigation, such a methodology is applied to better understand these properties in the context of regularized approaches. To this extent, linear stability analyses of two-dimensional models are proposed: the st...
The present work is dedicated to a better understanding of the stability properties of regularized lattice Boltzmann (LB) schemes. To this extent, linear stability analyses of two-dimensional models are proposed: the standard Bhatnagar-Gross-Krook (BGK) collision model, the original pre-collision regularization and the recursive regularized model,...
The lattice Boltzmann method (LBM) is known to suffer from stability issues when the collision model relies on the BGK approximation, especially in the zero viscosity limit and for non-vanishing Mach numbers. To tackle this problem, two kinds of solutions were proposed in the literature. They consist in changing either the numerical discretization...
The present study proposes a highly accurate lattice Boltzmann direct coupling cell-vertex algorithm, well suited for industrial purposes, making it highly valuable for aeroacoustic applications. It is indeed known that the convection of vortical structures across a grid refinement interface, where cell size is abruptly doubled, is likely to genera...
The present study focuses on the unphysical effects induced by the use of non-uniform grids in the lattice Boltzmann method. In particular, the convection of vortical structures across a grid refinement interface is likely to generate spurious noise that may impact the whole computation domain. This issue becomes critical in the case of aeroacousti...
A barotropic counterpart of the well-known convected vortex test case is rigorously derived from the Euler equations along with an athermal equation of state. Starting from a given velocity distribution corresponding to an intended flow recirculation, the athermal counterpart of the Euler equations are solved to obtain a consistent density field. T...
The lattice Boltzmann method (LBM) is known to suffer from stability issues when the collision model relies on the BGK approximation, especially in the zero viscosity limit and for non-vanishing Mach numbers. To tackle this problem, two kinds of solutions were proposed in the literature. They consist in changing either the numerical discretization...
This thesis provides an investigation on the use of lattice Boltzmann methods to treat turbomachinery secondary cooling systel flows. The combination of complex physical phenomena (rotating environment with high temperature fluctuations) gives rise to unsteady, non-axisymmetric structures with a priori unknown periodicity. Their modelling, required...
Abstract submitted to the DSFD conference (Bangalore, 22-26 July, 2019)
An extension of the von Neumann linear analysis is proposed for the study of the discrete-velocity Boltzmann equation (DVBE) and the lattice Boltzmann (LB) scheme. While the standard technique is restricted to the investigation of the spectral radius and the dissipation and dispersion properties, a new focus is put here on the information carried b...
Several collision operators have been proposed to overcome stability issues encountered by the lattice Boltzmann method (LBM), when high-Reynolds and/or moderate to high-Mach number flows are simulated. The present work focuses on the generalization of one of them: the regularized collision model. It relies on the Hermite polynomial expansion of ve...
A lattice Boltzmann method (LBM) with enhanced stability and accuracy is presented for various Hermite tensor-based lattice structures. The collision operator relies on a regularization step, which is here improved through a recursive computation of non-equilibrium Hermite polynomial coefficients. In addition to the reduced computational cost of th...
This paper reports the investigations done to adapt the Characteristic Boundary Conditions (CBC) to the Lattice-Boltzmann formalism for high Reynolds number applications. Three CBC formalisms are implemented and tested in an open source LBM code: the baseline local one-dimension inviscid (BL-LODI) approach, its extension including the effects of th...
AFLoNext is a project of four years duration, funded by the European Commission within the Seventh Framework Programme. The project's main objectives are proving and maturing highly promising ow control and noise reduction technologies for novel aircraft configurations, to achieve a big step forward towards improved aircraft performance and thus re...
Projects
Projects (3)
Towards extending the capabilities of LBM to reactive and compressible flows.
This project is dedicated to the comparison of the most common collision models used to stabilize lattice Boltzmann method (LBM) in the zero-viscosity limit. While most comparisons are based on numerical test cases, the present work focuses on the search of both their fundamental discrepancies and similarities. Several steps will be followed to achieve this goal: (1) derivation of mathematical deviations between models, (2) evaluation of their linear stability domain, (3) further confirmation using academic test cases and finally (4) quantitative validations based on industrial-level high-fidelity simulations of high-Reynolds number flows.
This online course aims to provide engineers, MS and PhD students a basic, but essential, understanding of the LBM.
Three major learning objectives were chosen, and allowed to design four weeks of online courses. In our opinion, it was mandatory that at the end of the SPOC (small private online course), participants would be able to:
(i) evaluate the relevance of using LBMs for a given case (benefits and limitations as compared to standard Navier-Stokes-Fourier (NSF) solvers),
(ii) choose the appropriate lattice and equilibrium distribution function depending on physical phenomena of interest, and
(iii) explain the numerical efficiency of LBMs (wall-clock time and accuracy) with respect to standard NSF solvers.
More details are available at https://cerfacs.fr/en/fundamentals-of-lattice-boltzmann-method/
