Pulsating Flow through a Tapered Curved Tube.

Abstract

An experimental investigation of pulsating flow through a tapered curved tube is presented to study the blood flow in the aorta. The experiments are performed in a U-tube with the curvature radius ratio of 3.5 and including 50 percent reduction in the cross-sectional area between the inlet and the exit of the curved section. Laser Doppler velocity measurements are made for the Womersley number of 10, the mean Dean number of 400 and the flow rate ratio of 1. Flow visualizations are used to investigate qualitatively the nature of the flow, complementing the quantitative LDV measurements. The velocity profiles for the steady and pulsating flows in the tapered U-tube are compared with the corresponding results in a U-tube having a uniform cross-section. The striking effects of the tapering on the flow are exerted on the axial velocity profiles in the section from the latter half of the bend to the neighborhood of the inlet of a downstream tangent. A depression phenomena in the velocity profile appears at the position of smaller bend angle Ω and the degree of the depression against the cross-sectional averaged velocity is reduced. Strong secondary fluid motions occur near the bend exit and that leads a velocity profile to depress weakly in the downstream tangent. The value of βm which indicates a uniformity in the velocity profiles decreases with an increase of Ω, but it rapidly increases just after the bend exit.