Vortex shedding in steady flow through a model of an arterial stenosis andits relevance to mural platelet deposition

In this study, the development of unsteady vortical formations in the separ ated flow region distal to a stenosis throat is presented and compared with the platelet deposition measurements, to enhance our understanding of the mechanisms involved in platelet kinetics in flowing blood. Qualitative and quantitative flow visualization and numerical simulations were performed in a model of a streamlined axisymmetric stenosis with an area reduction of 8 4% at the throat of the stenosis. Measurements were performed at Reynolds n umbers (Re), based on upstream diameter and average velocity, ranging from 300 to 1800. Both the digital particle image visualization method employed and the numerical simulations were able to capture the motion of the vortic es through the separated flow region. Periodic shedding of vortices began a t approximately Re=375 and continued for the full range of Re studied. The locales at which these vortices are initiated, their size, smd their life s pan, were a function of Re. The numerical simulations of turbulent flow thr ough the stenosis model entailed a detailed depiction of the process of vor tex shedding in the separated flow region downstream of the stenosis. These how patterns were used to elucidate the mechanisms involved in blood plate let kinetics and deposition in the area in and around an arterial stenosis. The unsteady flow development in the recirculation region is hypothesized as the mechanism for observed changes in the distribution of mural platelet deposition between Re =300, 900, and 1800, despite only a marginal variati on in the size and shape of the recirculation zone under these flow conditi ons. (C) 1999 Biomedical Engineering Society. [S0090-6964(99)00306-9].