Passive flow/noise control of a cylinder using metal foam
Metal foam has been proved to be an easy to implement, light weight and inexpensive passive flow control method which can be used to reduce vortex generation without the need of external sensors or actuators. An experimental analysis was performed on the effect of a metal foam coating on the flow around a cylinder and its sound generation. Laser Doppler Anemometry (LDA) and pressure tapping measurements were employed to investigate the effect of the application of a porous coating on the surface pressure distribution, wake pattern, and vortex shedding, while noise measurements were performed to test its performance in noise reduction. The metal foam coating reduced the turbulence intensity behind the cylinder, with stabilized shear layers detaching from the cylinder and suppressing the vortex shedding. The entrainment layers flowing through the metal foam filled the low pressure region generated in the leeward, increasing the base pressure and reducing the pressure drag coefficient by 20\ Noise results showed that the tonal noise identified in the bare cylinder matching the vortex shedding frequency was suppressed when the porous coating was applied given the disruption of the vortical structures.