Effect of Trailing-Edge Vortex Shedding on Rotor Noise Using High-Fidelity Numerical Simulations

This study presents numerical predictions of the aeroacoustics of a hovering ideally twisted rotor employing the NACA 0012 airfoil. Delayed-Detached Eddy Simulations using OVERFLOW are coupled with PSU-WOPWOP to evaluate broadband noise. Additionally, the spatiotemporal behavior of dominant acoustic sources is investigated using Spectral Proper Orthogonal Decomposition, which reveals high-energy coherent structures associated with distinct frequencies. Multiple cases are simulated to investigate the effects of trailing-edge thickness, turbulence models, and collective pitch settings. Cases exhibiting trailing-edge vortex shedding (TE-VS) at spanwise locations with significant blade–wake interactions (BWI) show substantial increases in high-frequency noise. This is attributed to the amplification of TE-VS-induced surface pressure fluctuations by BWI, resulting in strong upstream acoustic propagation toward the leading edge. In contrast, cases without TE-VS do not exhibit this upstream propagation, even when BWI is present. Furthermore, laminar boundary-layer vortex shedding noise is predicted using the Langtry–Menter 2015 transition model. Hydrodynamic instabilities originating in the laminar boundary layer are observed interacting with the trailing edge. The scattering of the instability waves along with vortex shedding generates upstream-propagating acoustic waves. Finally, increasing the collective pitch reduces the strength of TE-VS but leads to elevated BWI noise due to the formation of secondary vortices that surround tip vortex cores. These results demonstrate that accurate resolution of these turbulent structures is critical for the prediction of rotor broadband noise.