Experimental and numerical studies were made of the secondary flow induced in fully developed oscillatory laminar flow in a curved circular pipe. Photographs of traces of nylon particles suspended in water were taken systematically with Womersley numbers α = 5.5 ∼ 28 and oscillatory Dean numbers D = 40 ∼ 500. The secondary flow velocity component and the location of the vortex eye were obtained from the photographs. The experimental results were checked with the numerical ones and the variations of the secondary flow pattern with the Dean and Womersley numbers were analysed based on both results. These results suggest that secondary flows can be classified into five patterns.

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It is well known that the uid dynamics of arterial blood ow plays an important role in arterial diseases. Periodic blood ow through a stenosed tube was analyzed numerically. The bi-viscosity model is used as a constitutive equation for blood, and the ow is assumed to be periodic, incompressible and axisymmetric. E ects of pulsation and the rheological property of blood are considered. The ow pattern, separated region and the distributions of pressure and shear stress at the wall are obtained. The results show that the non-Newtonian property reduces the strength of the vortex downstream of stenosis and has considerable in uence on the ow even at high Stokes and Reynolds numbers, provided that pulsatile ow has a stagnant period.

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The fully developed periodic laminar flow of incompressible Newtonian fluids through a pipe of circular cross section, which is coiled in a circle, was simulated numerically. The flow patterns are characterized by three parameters: the Womersley number Wo, the Dean number De, and the amplitude ratio beta. The effect of these parameters on the flow was studied in the range 2.19 < or = Wo < or = 50.00, 15.07 < or = De < or = 265.49 and 0.50 < or = beta < or = 2.00, with the curvature ratio delta fixed to be 0.05. The way the secondary flow evolved with increasing Womersley number and Dean number is explained. The secondary flow patterns are classified into three main groups: the viscosity-dominated type, the inertia-dominated type, and the convection-dominated type. It was found that when the amplitude ratio of the volumetric flow rate is equal to 1.0, four to six vortices of the secondary flow appear at high Dean numbers, and the Lyne-type flow patterns disappear at beta > or = 0.50.