Coronary arterial dynamics computation with medical-image-based time-dependent anatomical models and element-based zero-stress state estimates

We propose a method for coronary arterial dynamics computation with medical-image-based time-dependent anatomical models. The objective is to improve the computational analysis of coronary arteries for better understanding of the links between the atherosclerosis development and mechanical stimuli such as endothelial wall shear stress and structural stress in the arterial wall. The method has two components. The first one is element-based zero-stress (ZS) state estimation, which is an alternative to prestress calculation. The second one is a "mixed ZS state" approach, where the ZS states for different elements in the structural mechanics mesh are estimated with reference configurations based on medical images coming from different instants within the cardiac cycle. We demonstrate the robustness of the method in a patient-specific coronary arterial dynamics computation where the motion of a thin strip along the arterial surface and two cut surfaces at the arterial ends is specified to match the motion extracted from the medical images. © 2014 The Author(s)

FIC/FEM formulation with matrix stabilizing terms for incompressible flows at low and high Reynolds numbers

The final publication is available at Springer via http://dx.doi.org/10.1007/s00466-006-0060-yWe present a general formulation for incompressible fluid flow analysis using the finite element method. The necessary stabilization for dealing with convective effects and the incompressibility condition are introduced via the Finite Calculus method using a matrix form of the stabilization parameters. This allows to model a wide range of fluid flow problems for low and high Reynolds numbers flows without introducing a turbulence model. Examples of application to the analysis of incompressible flows with moderate and large Reynolds numbers are presented.Peer ReviewedPostprint (author's final draft

Artificial boundaries and formulations for the incompressible Navier-Stokes equations. Applications to air and blood flows.

International audienceWe deal with numerical simulations of incompressible Navier-Stokes equations in truncated domain. In this context, the formulation of these equations has to be selected carefully in order to guarantee that their associated artificial boundary conditions are relevant for the considered problem. In this paper, we review some of the formulations proposed in the literature, and their associated boundary conditions. Some numerical results linked to each formulation are also presented. We compare different schemes, giving successful computations as well as problematic ones, in order to better understand the difference between these schemes and their behaviours dealing with systems involving Neumann boundary conditions. We also review two stabilization methods which aim at suppressing the instabilities linked to these natural boundary conditions

Computational Methods for Parachute Aerodynamics

We highlight some recent methods developed by the Team for Advanced Flow Simulation and Modeling http://www.mems.rice.edu/TAFSM/ for computation of parachute aerodynamics and fluid-structure interactions. This class of problems involve several computational challenges, including computation of unsteady long-wake flows generated by cargo aircraft carrying paratroopers and the affect of that unsteady wake on a parachute crossing it, as well as parachute aeromechanics simulations that take into account the changes in the parachute shape. Among the numerical methods we have developed to address these challenges are: a multi-domain method for computation of long-wake flows and flow around objects placed in such wakes, methods for the simultaneous solution of the fluid and structural mechanics equations governing the aeromechanics of a parachute. and advanced mesh moving methods. Our presentation here includes numerical examples that demonstrate the new computer simulation capabilities offered by the methods we have developed

A node-numbering-invariant directional length scale for simplex elements

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