Keywords: fluid-structure interaction, atherosclerosis, finite volume method, deformation profiles, polyurethane rubber arteries.

Atherosclerosis is a chronic medical condition in which thickening and loss in the elasticity of the artery wall leads to impaired blood circulation [1]. Cholesterols, lipids and other proliferating cells accumulate at localised regions within the artery wall. This has the effect of stiffening and thickening the wall at that point. The presence of an emerging plaque should effect the deformation of and stresses generated within the artery wall to such an extent that it should be possible to detect this disease whilst still in its early stages. The hypothesis under investigation in this work is that an altered deformation profile because of stiffening and thickening of the artery wall is an early indicator of the disease.

In order to test this hypothesis a combined experimental and numerical investigation into the behaviour of mock arteries is being carried out. Two mock arteries are considered, a healthy and a diseased case. The mock arteries are made from polyurethane rubber tubing. The experimental work aims to provide clear evidence of the effects of the diseased region on the deformation of the mock artery and at the same time provide verification data for numerical predictions.

The mock arteries have been subjected to an incremental increase in pressure up to a maximum value of 20kPa and the diameter measured at each pressure level. The diameter has been measured at a number of locations along the axial length of the tube. These experiments have been simulated using a finite volume solver; OpenFoam-1.2. The effect of the thickened patch under the action of dynamic fluid pressures has also been investigated. Three physiologically realistic pressure waveforms were applied to the fluid inlet of the healthy and the diseased mock artery. The waveforms were selected because the arteries they were measured in are particularly susceptible to plaque formation.

The thickened patch has been found to have a significant effect on the deformation and stresses of the mock artery. It has been shown experimentally that a thickened patch causes a reduction in the radial displacements in the patched section of tube, under a constant fluid pressure. The numerical simulations predict a decrease in hoop stress in the vicinity of the patch. The simulations under predict the decrease in radial displacement in the thickened region. This may be due to some non-uniformity in the tube's wall thickness. Under the action of physiologically realistic pressure waveforms the effect of the thickened patch is also pronounced. The patch causes a reduction in the displacements, strain and stress within the wall. The effect on the stress is greatest. For all flow conditions examined the effect on the flow field has been found to be negligible.

1

C.K. Glass and J.L. Witsum, "Atherosclerosis: The Road Ahead", Cell, 104, 503-516, 2001. doi:10.1016/S0092-8674(01)00238-0

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