Vortex enhancement in blood flow through stenosed and locally expanded tubes

It is well known that fluid dynamical phenomena in arterial blood flow can play an important role in arterial diseases. Periodic blood flow through st enosed and locally expanded tubes is analyzed numerically. The fluid is ass umed to be non-Newtonian and incompressible, and the flow is assumed to be periodic in time and axisymmetric. It is found that the vortex downstream o f stenosis or expansion becomes strongest at a certain frequency of pulsati on. This phenomenon is called vortex enhancement in this paper. The flow pa ttern, separated region and the distributions of pressure and shear stress on the wall are obtained. The results show that the vortex enhancement occu rs in both tubes. The vortex enhancement occurs where the difference betwee n the adverse pressure and the friction on the wall is a maximum. (C) 2000 The Japan Society of Fluid Mechanics and Elsevier Science B.V. All rights r eserved.