| Vortex shedding is a well-known unsteady fluid-dynamic phenomenon occurring in a variety of flows in nature including stenosed blood vessels. The current hypotheses regarding the origin of vortex shedding do not apply for the internal flow in a partially constricted two-dimensional channel. As a result, we postulate a novel mechanism to explain the origin of vortex splitting and shedding in this geometry.;Numerical simulations of the unsteady, two-dimensional, incompressible Navier-Stokes equations are performed in a channel having a constriction modeled by a two-parameter Gaussian distribution on both channel walls. Reynolds numbers from 1 to 3000 based on inlet half-channel height and mean inlet velocity and constriction ratios of 0.25, 0.5 and 0.75 are considered.;The Navier-Stokes solutions are observed to experience a number of bifurcations including unsteady behavior with shear-layer fluctuations and vortex shedding downstream of the constriction. A sequence of events is presented describing how a sustained shear layer instability leads to the unsteady vortex shedding phenomenon via a convective instability and a proposed streamwise pressure-gradient mechanism.;In addition, a global linear stability analysis is performed on several stationary Navier-Stokes solutions to determine the long-term temporal behavior of small amplitude perturbations.;Finally, the implications of this research on the hemodynamics in the cephalic vein and potential failure of the brachiocephalic fistula are addressed. |
