Numerical study of pulsatile channel flows undergoing transition triggered by a modelled stenosis

Abstract

In this research, we numerically investigate the physics of pulsatile flows confined within a 3-dimensional channel with a modelled stenosis formed eccentrically on the upper wall using the method of large-eddy simulation (LES). An advanced dynamic nonlinear subgrid-scale stress model was utilized to conduct numerical simulations and its predictive performance was examined in comparison with that of the conventional dynamic model. The Womersley number tested in the simulation was fixed at 10.5 and the Reynolds numbers tested were set to 750 and 2000, which are characteristics of human blood flows in large arteries. An in-house LES code, based on curvilinear Cartesian coordinates, has been developed to conduct the unsteady numerical simulations using three different grid systems. The physical characteristics of the flow field have been studied in terms of the resolved mean velocity, turbulence kinetic energy, viscous wall shear stress, resolved and subgrid-scale turbulent shear stresses, local kinetic energy fluxes between the filtered and subgrid scales, and turbulence energy spectra along the central streamline of the domain. Triggered by the stenosis, the flow field driven by the pulsatile inlet condition undergoes laminar-turbulent-laminar patterns in the streamwise direction. Correspondingly, the slope of the energy spectra deviates significantly from the well-known −5/3 law for the inertial subrange to reflect the transition in the flow patterns.