Methods to predict rotor trailing-edge noise using computational fluid dynamicsa)

This paper investigates various methods for predicting rotor turbulent boundary layer trailing-edge noise using computational fluid dynamics (CFD) in conjunction with Amiet's trailing-edge noise model. Three approaches are proposed and examined to obtain the boundary-layer parameters, which serve as key inputs to an empirical wall pressure spectrum model. The first approach directly extracts the boundary-layer parameters from 3D CFD solutions. The second approach derives the boundary-layer parameters from the sectional normal and chordwise forces. The third approach determines the boundary-layer parameters from the chordwise pressure coefficient distributions. Among these, the second approach is found to provide the most reliable and efficient predictions. The predictions demonstrate good agreement with experimental data for two rotor configurations under multiple operating conditions. Despite variations in thrust due to changes in collective pitch, the resulting change in the effective angle of attack is insufficient to induce substantial alterations in boundary-layer parameters, leading to low sensitivity to noise. However, airfoil selection, blade geometry, and rotation speed have a significant influence on the magnitude of trailing-edge noise.