This study investigates the effects of incidence angle on the aerodynamic response, wake structure, and associated aerodynamic sound radiation of flow past a square prism at Re=2.2×10^4. Two-dimensional unsteady simulations were first conducted for incidence angles ranging from α=0^∘ to 45^∘ to compare near-wake fluctuations, lift force characteristics, and the far-field acoustic properties predicted by the Lighthill acoustic analogy combined with the Ffowcs Williams-Hawkings (FW-H) equation. Two representative cases, α=0^∘ and 15^∘, were further examined using three-dimensional scale-adaptive simulation (SBES), to verify that the dominant frequency features identified in two-dimensional simulations, as well as the key acoustic radiation mechanisms, can be maintained in the three-dimensional wake environment. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) were adopted to analyze the frequency components corresponding to typical wake structures, and the Lighthill-based FW-H acoustic prediction framework was introduced to quantitatively correlate the near-field turbulent flow fluctuations with the far-field aerodynamic noise directivity and spectral distribution. The results show that the incidence angle significantly influences both the strength and spatial distribution of streamwise velocity fluctuations in the shear layers, leading to two distinct spectral patterns in the wake, defined as the harmonic-spectrum and dispersed-spectrum patterns, which further determine the energy concentration and propagation characteristics of the radiated aerodynamic sound. For α=15^∘-37.5^∘, the wake response exhibits a harmonic-spectrum pattern, with spectral energy concentrated at the primary vortex-shedding frequency and its harmonics, producing a typical tonal-dominated aerodynamic noise radiation with distinct discrete peaks in the far-field sound pressure level spectrum. By contrast, for α=0^∘, 7.5^∘, and 45^∘, the wake response shows a dispersed-spectrum pattern, in which non-primary frequency components are more broadly distributed, resulting in a relatively wider-band, low-amplitude sound radiation characteristic without prominent tonal peaks. The three-dimensional SBES results confirm that the main spectral patterns captured in two-dimensional simulations, as well as the corresponding acoustic radiation characteristics predicted by the FW-H approach, remain recognizable in the fully developed three-dimensional wake.

Cai Jiancheng is a professor at the College of Engineering, Zhejiang Normal University. He received his B.S., M.S., and Ph.D. degrees in Power Engineering and Engineering Thermophysics from the School of Energy and Power Engineering, Xi'an Jiaotong University. He also served as a visiting scholar at the School of Engineering, the University of Western Australia. Professor Cai has long been dedicated to research in fluid mechanics, flow-induced noise, mechanical vibration and noise control, and computational fluid dynamics. He has presided over 3 projects funded by the National Natural Science Foundation of China and 4 projects supported by the Zhejiang Provincial Natural Science Foundation, along with many industry-sponsored research initiatives. His work has been published in leading international journals such as Physics of Fluids, Ocean Engineering, and the Chinese Journal of Acoustics. As an active member of Acoustical Society and Society of Engineering Thermophysics of Zhejiang Province s, Professor Cai maintains close collaborations with industry, applying his expertise to solve practical challenges in vibration reduction and noise control, especially for fluid machinery.