Hydrodynamic characteristics and noise reduction mechanism of a wave leading hydrofoil placed in the wake of a cylinder

Abstract

We have investigated the hydrodynamic and acoustic performance of a hydrofoil with a wave leading edge that is being ingested in a cylindrical wake, to explore the interaction and noise reduction mechanism with the use of near flow field and far field noise decoupled prediction methods of large eddy simulation (LES) and Ffowcs Williams-Hawkings (FW-H). Our results indicate that the wave leading edge has minimal effect on the hydrodynamic performance, however, it has demonstrated the ability to significantly improve the acoustic performance. Through the comparison of sound pressure level (SPL) and acoustic directivity, we have observed that the wave leading edge can significantly reduce the broadband noise in the far field. This is due to its ability to break the large-scale structure of the incoming flow, which weakens the direct impact and therefore reduces the tone noise. Additionally, the interaction between the broken vortex and the boundary layer around the hydrofoil surface is weakened, leading to a reduction in surface pressure pulsation and broadband noise intensity. The wave structure primarily affects the flow structure near the leading edge, resulting in a reduction in flow disturbance and sound source intensity, and an improvement in the acoustic feedback loop between the foil and the fore-cylinder.