Application of Actuator Line Model for Large Eddy Simulation of Rotor Noise Control

Abstract

A hybrid Large Eddy Simulation (LES)/Actuator Line Model (ALM) computational approach is employed to simulate the turbulent wake of a two-bladed rotor in hover. Validations are performed for the Knight and Hefner two-bladed rotor case with comparisons to previous LES predictions using the immersed boundary method, as well as hybrid RANS-LES using the Helios code. The Ffowcs-Williams Hawkings (FWH) acoustic analogy is then used for predicting rotor noise. Predictions from the combined LES/ALM/FWH model are next validated against recent PIV wake flow and acoustic measurements for a two-bladed rotor. Finally, the LES/ALM/FWH approach is exploited to demonstrate a novel way to explore active flow control strategies to reduce rotor noise by delaying flow separation and enabling a lower rate of rotation, resulting in lower noise while maintaining thrust.