Numerical study on passive flow and noise control for flow past cylinder by porous media coatings

Abstract

The present study investigates the flow around a uniform porous-coated cylinder under subcritical flow state (Re=5×104) through numerical analysis to explore the influence of porous media parameters on the wake flow and radiated noise of cylinders. A numerical approach that integrates large eddy simulation and the Ffowcs Williams–Hawkings acoustic analog method is employed and validated through comparison with existing experimental and numerical data. The research shows that the application of porous media not only significantly alters the flow pattern behind the cylinder, stabilizes the boundary layer separation from the cylinder surface, widens the wake width, and reduces the pressure fluctuations on the cylinder surface, but effectively suppresses vortex shedding in the wake region and enhances the base pressure on the leeward side, thereby reducing the drag coefficient and shedding frequency of the cylinder, which achieves the effects of drag reduction and noise mitigation. The present study found that when the covering angle on the leeward side of the cylinder was 300° and the coating thickness was 16 mm, the average drag coefficient decreased by 36.27% and the aerodynamic noise by 74.91%. Furthermore, when the permeability was 1.5×10−5 m2, the average drag coefficient decreased by 45.78% and the aerodynamic noise by 73.79%. Additionally, the comparative analyses of the overall sound pressure level show that though applying porous media does not alter the radiation mode of noise, it can reduce the sound source intensity. This study is expected to provide useful information for the flow and noise control of high-speed train pantograph structures.