Effect of Wall Motion on Arterial Wall Shear Stress

Abstract

The distribution of wall shear stress (WSS) in arteries is affected by both blood and wall motion. Most studies have ignored wall motion by assuming that the artery wall is rigid. To investigate the influence of wall motion we have solved the coupled fluid-solid problem in a straight homogeneous tube. The inlet boundary condition of the tube was given as a pulse of velocity imposed at the inlet of the tube upon a steady flow of Reynolds number 1000. A commercial code (Radioss, Altair Engineering) was used to solve the fluid-solid interactions. Two kinds of waves are generated on the wall by the pulse imposed in the inlet flow; a wave of longitudinal motion of the wall (the longitudinal wave) and a wave of radial motion of the wall (the elastic wave). The ends of the vessel are assumed to be fixed which results in the reflection of both waves. The longitudinal wall motion reduces the relative speed of the blood, reducing WSS by up to 0.5 Pa. The largest effect of wall motion occurs when the longitudinal and elastic waves coincide, where the peak WSS is reduced by 1.0 Pa, which is a significant fraction of the observed WSS. Thus we can say that the effect of wall motion is important in considering physiological response of arterial wall to the blood flow.

Keywords

• fluid-solid interactions
• wall shear stress
• wall motion
• longitudinal wave
• elastic wave
• atherosclerosis
• large artery