Blood flow in tapered tubes with biorheological applications.

A steady laminar flow of blood in a uniform tapered tube has been examined. Blood rheology is assumed to be described by a polar fluid. The analytical expressions for velocities (both axial and radial), total angular velocity, wall shear and pressure drop have been obtained. In literature, the parameters N (coupling number) and L (length ratio) have been chosen independently. But, in the present analysis, it is found that they are interrelated. Variation of the flow variables with suspension concentration and tapered angle have been investigated. Some of the theoretical models for the flow through tapered tubes have been critically examined. The pressure-flow relationship has been studied numerically over the flow rate range 0.01-0.1 cc/sec and compared with experimental results. It has been shown that the existing experimental results are for the tapered tubes of larger diameter which correspond to the flow under Newtonian conditions. Finally, some biological implications and future developments of this theory have been indicated.