An experimental study of pulsatile flow in a curved tube.

Abstract Experimental measurements of axial velocity profiles at various cross-sections in a curved tube due to a pulsatile flow of uniform entry are reported. The curved tube with the radius of 1.5 cm and radius-radius of curvature ratio of 0.1 was mounted in a mock-circulatory system which simulates physiological pulsatile flow for a blood-analog fluid. The experiments were carried out for a time-averaged Reynolds number of 1019, a Dean number of 322 and a Womersley parameter of 21.89. Flow visualization was used to qualitatively investigate the nature of the flow, complementing the quantitative measurements made by hot-film anemometry. The fluid in the curved tube accelerated and moved downstream during the forward flow duration (systole) in the pulsatile flow cycle. However, during the remainder of the cycle (diastole), recirculation occurred, with fluid particles near the outer wall of the curved tube continuing their motion downstream, and fluid particles near the inner wall moving in a retrograde fashion back upstream. Immediately past entry into the curved tube, the maximum axial velocity was observed near the outer wall of the tube. The maximum velocity shifted towards the inner wall at the apex of the curve and shifted back towards the outer wall in the far downstream region. The velocity profiles for the pulsatile flow are compared with the corresponding results for steady flow at each cross-section for a Dean number of 569. The implications of the results with respect to the hemodynamic theories of atherogenesis are briefly discussed.