Aerodynamic Noise Generated in Three-Dimensional Lock-In and Galloping Behavior of Square Cylinder in High Reynolds Number Turbulent Flows

The flow dynamics and aeroacoustics propagation for flow-induced vibration system consisting of three-dimensional flow past an elastically-mounted square cylinder are investigated using the Ffowcs Williams–Hawkings method and detached eddy simulation model for the first time. Previous experimental and numerical data are compared with the results obtained by models implemented in this work to validate the correctness of the present hybrid modeling. The representative reduced velocities, spanning from lock-in to galloping regimes of concerned configurations, are chosen for investigation with the Reynolds number fixed at 6.67 × 10⁴. The structural response of the present fluid-induced vibration (FIV) system exhibits the feature of “vortex-induced vibration–galloping instability,” and the pattern of wake dynamics is determined into “wake-locked instability” or “wake-unlocked instability“ based on the specific vortex-shedding behavior. Specifically, the wake dynamics of the FIV system at a reduced velocity of 30 involve spatially concentrated vortex-shedding behaviors compared to smaller reduced velocities, leading to the corresponding higher-frequency components in the pressure spectrum. Furthermore, the enhancement of structural amplitude leads to the increasing energy of acoustics pressure, but structural amplitude is not the only decisive factor in determining the power of sound pressure level. The impermeable surface could provide the turbulence-induced noise source which increases the power of broadband frequency. The phase differences of acoustics pressure fluctuation between loading and thickness noise components will suppress the overall noise energy and the variation of phase differences is correlated to the position of sound monitors as well as reduced velocities.