Relationship between vortex shedding noise and remotely-sensed surface pressure fluctuations of a structured porous-coated cylinder

Tonal noise suppression of a cylinder placed in uniform flow has been achieved, to some extent, by coating it with a structured porous material as a form of passive flow and noise control. A previously studied structured porous-coated cylinder is investigated in an anechoic wind tunnel to determine the relationship between the far-field vortex shedding noise and the pressure recorded on the outer porous surface. To date, no experimental studies have been conducted on the surface pressure of any type of porous-coated cylinder. Acoustic measurements are obtained using an equispaced microphone arc array and simultaneously unsteady surface pressure fluctuations are obtained around the cylinder mid-span circumference using remote-sensing techniques. By obtaining simultaneous time-dependent signals, more light is shed on the underlying noise-reduction mechanism of the structured porous-coated cylinder. In this paper, strong relationships between surface pressures and acoustic signals are revealed at the vortex shedding frequency. A spatio-temporal relationship between surface pressure and vortex shedding phenomena is also presented that helps explain the role of the structured porous media in passive flow and noise control.