Numerical study on hydrodynamic performance and flow noise of a hydrofoil with wavy leading-edge

Flow control based on bionics provides new research ideas for noise reduction. As one of the flow control methods, the wavy leading edge (WLE) inspired by the leading edge tubercles of the humpback whale is proposed in this paper. The hydrodynamic performance and flow noise of a National Advisory Committee for Aeronautics 0020 hydrofoil subjected to three WLEs are numerically investigated. A hybrid numerical method of large eddy simulation combined with the Ffowcs Williams-Hawkings equation is adopted to obtain the unsteady flow properties and predict the far-field noise. At a Reynolds number of 3.05 × 10⁵, the simulation results show that the addition of WLEs can reduce the lift coefficient fluctuation but will increase the drag coefficient slightly. In addition, the WLE can reduce the OverAll Sound Pressure Level of the hydrofoil by up to 7.28 dB. The analysis of the flow features shows that the WLE can reduce the pressure fluctuation on the hydrofoil surface, which is directly beneficial to the noise reduction. Moreover, the WLE enhances the spanwise flow of the hydrofoil, produces streamwise vortices, and reduces the spanwise coherence coefficient at both the leading edge and trailing edge.