Aerodynamic noise reduction of circular cylinder by longitudinal grooves

摘要

Aerodynamic noise reduction of a circular cylinder using longitudinal grooves was experimentally investigated by measuring noise and velocity fields with a microphone and particle image velocimetry, respectively. Experiments were performed in an acoustic wind tunnel operating at subcritical Reynolds numbers, Re = (2-6) x 10(4). The results indicate that the aerodynamic noise from a circular cylinder decreased by 8 and 5 dB compared with a smooth circular cylinder when the ratio of groove-depth to cylinder-diameter is set to 0.010 and 0.017, respectively. Velocity field measurements suggested a downstream shift in flow separation on the circular cylinder and a corresponding decrease in turbulence intensities near the wake of the grooved circular cylinder. Furthermore, the spanwise correlation of streamwise velocity fluctuations decreased near the wake of the grooved circular cylinder. These results demonstrated that aerodynamic noise reduction and variation in turbulence structure occurred in circular cylinders with longitudinal grooves at subcritical Reynolds numbers.