Mixing enhancement in flow past rectangular cavities as a result of periodically pulsed fluid motion

Abstract

Periodic elimination of the shear layer separating the mainstream and recirculatory regions in flow through a multicavity channel is possible by imposing a pulsatile flow component on an otherwise steady flow. Numerical and experimental results are correlated to show that pulsing the flow during half of a cycle leads to the destruction of the trapped vortex while simultaneously generating its replacement. During the other half of the cycle, when there is only steady flow, a new vortex grows to fill the cavity and protrudes into the mainstream, thus further enhancing mainstream and cavity mixing. The fluid motion is characterized by three nondimensional parameters: a Reynolds number based on the steady velocity component; a Reynolds number based on the unsteady velocity component; and a Strouhal number based on the frequency of oscillation and the unsteady velocity component. >