Numerical study of flow-sound correlation mechanism and sound source distribution for NACA0012 hydrofoil

Hydrofoil is a simplified model of the propeller. Its lifting surface is also widely used in the submarine sail, rudder and other structures. Focus on hydrofoil sound source distribution and flow-sound correlation mechanism, NACA0012 hydrofoil is selected as the research object. Large eddy simulation (LES) and acoustic analogy is used to study the flow and sound characteristics. Dual-mesh technology is applied for accelerating the computation. The numerical results are validated by experiments. It is found that the computational efficiency is improved by more than 30 times with no loss of accuracy using dual-mesh technique. Cross spectrum, third-generation vortex identification technique and DMD are used to analyze the mechanism of wall pressure fluctuation and vortex structure on the radiated noise. By calculating the cross-spectral correlation coefficients, it is found that the correlation is stronger at the nth order peak frequency. Both of dipole and wall pressure have extreme values in the suction and lifting direction. With dynamic mode decomposition (DMD), it is found that the vortices are similar to the dominant mode of the Lighthill source. The peak frequency of quadrupole corresponds to the high-energy mode of the vortex shedding.