NUMERICAL STUDY OF THE STRUCTURE AND LOCAL TURBULIZATION OF THE FLOW IN A BLOOD VESSEL WITH A ONE-SIDE STENOSIS

Abstract

Results of large eddy simulation of three-dimensional flow in a model of the blood vessel with a one-side 70% stenosis at a Reynolds number of 1800 are presented. The Germano-Lilly model was used for subgrid viscosity evaluation. It has been established that the time-averaged flow behind the stenosis is characterized by the presence of two zones of recirculation flow: (i) an extensive zone that arises just behind the stenosis and has a length of about five vessel diameters, and (ii) a relatively small zone positioned near the opposite wall at a distance of about four calibers from the stenosis center. When a high-velocity jet is formed within the stenosis region, a secondary flow also forms as a pair of counter-rotating vortices, which are similar to the Dean vortices in a curved tube flow. The vortex pair arisen in the stenosis leads to a bifurcation of the high-velocity jet and induces also a cross-flow in the reverse flow zone behind the stenosis. The cross-flow almost completely disappears at a distance of less than ten calibers from the stenosis. Hydrodynamic instabilities that are peculiar to the high-gradient mixing layer, which is formed at the boundary of the jet and the reverse flow zone, initiate turbulence occurring with formation of three-dimensional vortex structures of different scales. These structures fill the entire cross-section of the vessel near the flow reattachment point. Turbulent shear stresses are significant in magnitude only at a flow section of about four-caliber length in the vicinity of the reattachment point. Further downstream, the flow relaminarises.

Keywords

• blood flow
• stenosis
• turbulence
• numerical simulation
• large eddy simulation