Noise reduction of a circular cylinder through varied porous coating configurations

An experimental investigation was carried out to explore the impact of various porous coating configurations on the vortex-induced noise generated by a circular cylinder. The windward, leeward, and top sides of a circular cylinder, as well as its entire circumference, were coated with structured porous media. Remote-sensing method was utilized to measure near-field pressure at the outer diameter of the porous-coated cylinders, synchronized with far-field noise, while planar particle velocimetry captured the wake velocity field. Results revealed that coating the entire circumference of the cylinder with porous material yielded the most significant reduction in far-field noise. Exceptionally, coating the top side of the cylinder demonstrated higher noise reduction compared to windward and leeward coating configurations. The application of porous coating extended shear layers further along the flow before rolling up into vortices, initiating vortex shedding downstream. This led to a reduction in the energy content of flow structures near the cylinder, resulting in weakened pressure fluctuations at the cylinder’s shoulders and, consequently, a reduction in far-field noise.