Abstracts - KTH Mechanics

Effects of the flexibility of the arterial wall on the wall shear
stresses in Abdominal Aortic Aneurysms
A. V. Salsac a, M. Fernández b, P. Le Tallec c and J. M. Chomaz d
As an abdominal aortic aneurysm forms and develops, large changes occur in the
composition and structure of the arterial wall, which result in its stiffening. So far,
most studies, whether experimental or numerical, have been conducted assuming the
walls to be rigid. A numerical simulation of the fluid structure interactions is
performed in different models of aneurysms in order to analyze the effects that the
wall compliance might have on the flow topology and on the dynamics of the wall.
The goal of the study is to quantify the changes induced by the wall compliance on the
spatial and temporal distributions of wall shear stresses. Of interest is also the
evaluation of the distribution of wall tension, which cannot be estimated in a rigid-wall
configuration. The results of the numerical simulations are compared with
measurements obtained experimentally in rigid models of aneurysms, which serve as
the reference case.
The numerical code couples a fluid solver (resolution of the incompressible Navier
Stokes equations in a ALE configuration) and a solid one (arterial wall modeled as a
non-linear shell) with a message passing library. Both symmetric and non-symmetric
models of aneurysms are considered, all idealistic in shape. The mechanical properties
of the aneurysm wall are varied in order to simulate their progressive stiffening. The
wall is fixed at its extremeties, preventing any displacement or rotation. A
physiologically correct flow rate is imposed at the inlet cross-section and the normal
stress at the outlet.
In the case of compliant walls, it is essential to reproduce a physiological pressure
field. The pressure within the model is shown to be strictly governed by the oulet
pressure condition, the flow dynamics having only a negligible effect. When using a
0D model for the outlet boundary conditions, we show that the wall elasticity leads to
a decrease in the mean value of the wall shear stresses that depends on the coefficient
of elasticity.
a
Mechanical Engineering Dept., University College London, London WC1E 7JE, England.
b
INRIA Rocquencourt, 78153 Le Chesnay Cedex, France.
c
LadHyX, Ecole Polytechnique, 91128 Palaiseau Cedex, France.
d
LMS, Ecole Polytechnique, 91128 Palaiseau Cedex, France.
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