Effect of a porous coating on the vortex shedding noise of a cylinder in turbulent flow

The effect of a porous coating on the vortex shedding noise of a circular cylinder under disturbed inflow conditions was examined experimentally. The measurements were performed on a cylinder coated with an open-porous foam as well as on a bare reference cylinder in a small aeroacoustic wind tunnel using grid-generated turbulence. The measurements were performed at Reynolds numbers based on outer cylinder diameter from 1.2.10(4) to 4.2.10(4). In laminar flow, the porous coating leads to a narrowing of the vortex shedding tonal noise peak as well as to a slight shift towards lower Strouhal numbers in this Reynolds number range. In turbulent flow, the present results show the clear trend that this shift towards lower Strouhal numbers is even more pronounced. In addition, the vortex shedding peak level decreases for the porous coated cylinder, an effect that, on average, is also stronger when the inflow is turbulent. (C) 2022 Elsevier Ltd. All rights reserved.