Direct numerical simulation of pulsatile flow in pipes

Abstract

This study presents data from direct numerical simulation (DNS) of pulsatile flow in a rigid smooth pipe approximating the blood flow condition in the human aorta. Since blood flow behaves in a laminar fashion in certain regions in the human aorta but turbulent in other regions, pulsatile flows are numerically studied in both laminar and turbulent flow regimes. Pure oscillatory simulations are carried out over a range of Womersley numbers (α = 1,5,10,15) in the laminar regime. Numerical velocity profiles and pressure-flow relationship from these results in the laminar regime are validated with the analytical solution. Blood flow inside an aorta is simulated by superimposing a mean pressure gradient component to an oscillatory pressure gradient. The mean Reynolds number based on bulk velocity is Re0 ≈ 5300 (equivalent to Reynolds number based on uτ, Reτ = 180) and the oscillatory-flow Reynolds number Rew is determined by the oscillatory component. The simulated flow driven by the total pressure gradient falls in the turbulent regime. An instantaneous flow field visualisation and mean statistics are presented and analysed. The pressure-flow relationship of turbulent flow is also investigated. Turbulent pipe flow with and without pulsation are compared and the effects of the oscillatory pressure gradient on the mean velocity and wall shear stress are demonstrated in this paper.