Biomedical subjects

Bastien Chopard

Publications and source records attributed to Bastien Chopard.

4 recordsLinked to original sources

PubMed2006

Two grid refinement methods in the lattice Boltzmann framework for reaction-diffusion processes in complex systems.

This paper studies the optimisation of a numerical model and a computer code to solve numerically reaction-diffusion processes in environmental or biological systems with complicated geometries and mixtures of reactions including time and spatial scales extending over several order of magnitude. In particular, we consider different grid refinement techniques in the framework of a lattice Boltzmann solver for reaction-diffusion systems. Two new grid refinement methods are proposed, which are both quantitatively good. The first method is based on the matching of the concentration profiles and fluxes across two adjacent sub-domains, while the second method is based on nested subgrids. The focus of our study is the trade off between accuracy and CPU time. We show how the different parameters of the method, such as the refinement factors, the location of the boundary between different grids or coupling methods at the interface affect the quality of the numerical solution and the efficiency of the method.

Journal Article↗

PubMed2005

LBGK method coupled to time splitting technique for solving reaction-diffusion processes in complex systems.

A new approach to numerically solve a reaction-diffusion system is given, specifically developed for complex systems including many reacting/diffusing species with broad ranges of rate constants and diffusion coefficients, as well as complicated geometry of reacting interfaces. The approach combines a Lattice Boltzmann (LB) method with a splitting time technique. In the present work, the proposed approach is tested by focusing on the typical reaction process between a metal ion M and a ligand L, to form a complex ML with M being consumed at an electrode. The aim of the paper is to systematically study the convergence conditions of the associated numerical scheme. We find that the combination of LB with the time splitting method allows us to solve the problem for any value of association and dissociation rate constant of the reaction process. Also, the method can be extended to a mixture of ligands. We stress two main points: (1) the LB approach is particularly convenient for the flux computation of M and (2) the splitting time procedure is very well suited for reaction processes involving association-dissociation rate constants varying on many orders of magnitude.

Chemical Industry↗

PubMed2003

Characterization of flow reduction properties in an aneurysm due to a stent.

We consider a lattice Boltzmann simulation of blood flow in a vessel deformed by the presence of an aneurysm. Modern clinical treatments involve introducing a stent (a tubular mesh of wires) into the cerebral artery in order to reduce the flow inside the aneurysm and favor its spontaneous reabsorption. A crucial question is to design the stent with suitable porosity so as to produce the most effective flow reduction. We propose a stent positioning factor as a characterizing tool for stent pore design in order to describe the flow reduction effect and reveal the several flow reduction mechanisms using this effect.

Aneurysm, Ruptured↗

PubMed2003

Theory and applications of an alternative lattice Boltzmann grid refinement algorithm.

This contribution proposes an alternative lattice Boltzmann grid refinement algorithm that overcomes the drawbacks that plague existing approaches. We demonstrate that this algorithm is accurate and applicable for all values of the relaxation time. We also show that this algorithm can significantly speed up the flow settlement process. By using a hierarchy of grid levels, the stationary regime can be approached up to a thousand times faster than with a single grid resolution.

Journal Article↗