Acoustic effects on aerodynamic characteristics of a surface-mounted square cylinder

The coupling between sound and flow likely influences the aerodynamics of bluff bodies, which deserves in-depth investigations. This paper presents a comprehensive experimental study of the effects of sound on the near wake flow and aerodynamic forces of a finite three-dimensional (3D) square cylinder in smooth flow and grid-generated turbulent flows. The study centers on the respective influences of a wider range of sound frequencies (1–2000 Hz) and sound pressure levels (60–100 dB) compared to previous studies. Employing a combination of particle image velocimetry and pressure measurements, the effects of sound on the aerodynamic characteristics, specifically, the near wake flow field, vortex shedding dynamics and pressure distributions are investigated. The spectral analysis and proper orthogonal decomposition analysis are conducted to gain deeper insights into the effects of sound on the coherent structures of the aerodynamic forces around the square cylinder. The results demonstrate that the influences of sound in modulating the wind pressure distributions on the cylinder are dependent on both the sound frequency and sound pressure level. The findings also highlight the occurrence of acoustic resonance and its impact on vortex-shedding behaviors and flow fields, demonstrating the sensitivity of these phenomena to specific sound frequencies and sound pressure levels. Furthermore, these sound-induced change phenomena can be weakened when turbulence is added to the approaching flows. The degree of this attenuation is found to vary depending on specific characteristics of a turbulent flow, such as turbulence intensities and integral length scales.