Simulation of oscillatory wall shear stress in channels with moving indentations

The aim of this paper is to study the effects of a periodically, excited wall on the oscillatory nature of wall shear stress (WSS) and flow structures. A non-Newtonian incompressible Navier-Stokes (N-S) solver with moving boundary was developed using Fasttalk language within the Fastflo environment. It was based on the methods of operator splitting and artificial compressibility with consideration to retain space conservation property. A two-dimensional channel having a dimension of a human femoral artery but with arbitrarily assigned wall movement was employed. The Newtonian version of the code was validated against published work by simulation of flow in this channel with time-varying upper and lower walls. Non-Newtonian models (approximately 45% haematocrit) of blood flow were performed for comparison. The code was then applied to a channel with a fixed, straight, upper wall and a moving indenting lower wall. Flow separation, stagnation, and unsteadiness were characteristic flow features observed in this study. The Power Law model showed higher shear-thinning effect at any time the frame produced the smallest vortices. The Casson model produced the highest WSS which was oscillatory in nature. When the upper wall was fixed, the indenting wall experienced almost twice as much as an induced oscillatory WSS as the rigid wall. The result also suggested that periodic wall movement is a mechanism of producing oscillatory WSS. This study may provide probable insights on atherogenesis, while the solution scheme may be useful in vascular biology. Copyright (C) 2002 John Wiley Sons, Ltd.