Control of aeolian tone from a square cylinder using periodic suction-blowing excitation at low Reynolds number using direct numerical simulation approach

Abstract

This study numerically investigates the impact of periodic suction-blowing excitation (SBE) on the aeolian tone generated by flow past a square cylinder at a Reynolds number (Re) of 100. Excitations are applied in three configurations: case I, with suction on the front and blowing on the rear of the square cylinder; case II, with suction on the top and bottom and blowing on the rear; and case III, with suction on the top and bottom and blowing on both the front and rear sides of the cylinder. The application of excitation significantly alters the flow and sound fields, streamlining the flow, reducing the size of separation bubbles, and weakening vortex strength, leading to a notable reduction in the time-averaged drag coefficient. Additionally, the dominant lift fluctuation dipole sound sources decrease, while drag-related dipole sound sources increase, corresponding to reduced lift fluctuations and increased drag fluctuations. These changes in sound sources alter both the direction of sound wave propagation and the intensity of the aeolian tone. Furthermore, the effects of excitation parameters, such as maximum amplitude and strip length, on the flow and sound fields are examined. Increasing the amplitude or strip length significantly reduces the average drag coefficient. Optimal parameters for case III result in a reduction in sound power by nearly 6 dB, shifting the predominant sound wave propagation from the normal to the axial direction, demonstrating the potential for controlling sound directivity and mitigating aeolian tone intensity through targeted excitation strategies.