Wall roughness effects on the supersonic flow over a circular cylinder

A comprehensive and systematic, computational investigation is presented on the effect of wall roughness on the supersonic flow over a circular cylinder with a Reynolds number of 500. Flow simulations are conducted using ANSYS Fluent. Wall roughness is modeled by a perturbation of the cylinder geometry with harmonic modes of varying amplitude and frequency. Validated smooth cylinder flow simulations for a range of Mach and Reynolds numbers with slip and no-slip wall serve as a reference. Roughness is shown to increase the effective diameter of the cylinder and the drag by displacing the outer flow along the peaks of the roughness elements. For lower frequencies, this effect is less pronounced than for higher roughness frequencies. While for smooth cylinders the vorticity is mostly generated by viscous shear forces, for rough cylinder the baroclinic vorticity generation is shown to be dominant and shown to determine the topology of the recirculating region.