Effects of Upstream Porous Treatments on the Hydrodynamic and Hydroacoustic Performances of a Hydrofoil

This paper presents numerical studies on the effects of upstream porous treatments on the hydrodynamic and hydroacoustic performances of a hydrofoil. The inflow velocity is 5 m/s and the chord-based Reynolds number is 2.5 × 107. A rapid turbulent boundary layer (TBL) noise prediction method is proposed by coupling the Reynolds-averaged Navier–Stokes (RANS) flow simulations, the Lee’s empirical wall pressure spectrum (WPS) model and the Howe’s trailing-edge noise model. This hybrid model is well validated against the experimental data. Using the developed noise prediction method, the effects of upstream porous treatments on the hydrodynamic and hydroacoustic performances are systematically studied, focusing on key parameters such as porous coverage area, porosity, pore diameter and half-porous configurations. The results generally indicate that the porous treatments can significantly reduce the mid-to-high-frequency noise, whilst slightly increasing the low-frequency noise. Within this parametric range, a larger porous coverage area yields more pronounced mid-to-high frequency noise reduction. Specifically, when the porous coverage accounts for 10% of the chord length, the mid-to-high frequency noise reduction reaches 14.3 dB; as the coverage expands to 25% of the chord, the noise reduction in this frequency band further increases to 35.2 dB. While smaller porosity and pore diameter enhance noise reduction, they incur greater hydrodynamic penalties. Within the scope of this study, the minimum porosity (φ = 0.55) and the minimum pore diameter (d = 0.1 mm) achieved mid-to-high frequency noise reductions of 19.1% and 17.3%, respectively, while the drag coefficient increased by 8.9% and 17.3%, respectively. Furthermore, the noise reduction is found to deteriorate with increasing angles of attack (AOAs). The wall shear stress and boundary layer thickness are also significantly affected by the porous treatments. This work provides rapid evaluations and can also be used for the optimization of porous treatments.