Experimental Investigation of Aerodynamic Noise and Wake Flow Produced by Porous-Coated Square Cylinders

Abstract

Periodic vortex shedding from square cylinders is a typical source of aerodynamically induced noise. One possible passive method to reduce this noise is the use of porous coatings, which have received a lot of interest from the scientific community in the past. In the experimental study described in the present paper, the noise generation and near-wake features of a square cylinder coated with an unstructured porous material was investigated in a small aeroacoustic wind tunnel at subsonic flow velocities. Two open-porous materials with different porosity and permeability were used. The results show that the selected porous coatings lead to a notable reduction of the vortex shedding tonal noise, to a shift of the corresponding vortex shedding Strouhal number as well as to an overall broadband noise reduction. These acoustic effects are accompanied by a reduction of both the mean flow velocity and the turbulence intensity in the wake of the porous-coated cylinders compared to a bare reference cylinder.