Surface Roughness Benefits in Open Cavity Flows

Abstract

In the current study, we report the effect of distributed roughness elements on the flow characteristics within a rectangular cavity using a series of high-fidelity eddy-resolving simulations. A cavity with a length to depth ratio (L/D) of 3 is considered. Simulations are carried out at a Mach number of 0.2 and Reynolds numbers of 7000 and 19300, based on the free-stream velocity and the depth of the cavity. The cavity flows generate undesirable low-frequency pressure fluctuations due to the vortex impingement over the trailing edge of the cavity. We explore the possibility of employing distributed hemispherical roughness elements as a passive flow control strategy towards suppressing these pressure fluctuations. The roughness elements, modeled using the immersed boundary method, are placed upstream of the cavity leading edge and distributed along the span. For a given roughness configuration, we studied the effect of varying Reynolds numbers on the flow features generated by the roughness elements and their interaction with the growth of the separated shear layer using instantaneous and time-averaged flow fields. The roughness elements are shown to effectively reduce the sound pressure level (SPL) up to 7dB for the test cases considered.