Rotorcraft Vibration and Noise Prediction Using a Unified Aeroelastic Analysis

A study of the combined helicopter noise and vibration problem was conducted. A refined aerodynamic model capable of calculating the unsteady surface pressure distribution on rotor blade/flap combinations is developed and coupled with an aeroelastic analysis simulation code. An acoustic prediction tool based on WOPWOP is combined with the aeroelastic analysis based on a flexible blade with coupled flap-lag-torsional dynamics. This unified analysis program is validated with experimental data. The acoustic environment of the helicopter is characterized by microphones mounted on the rotorcraft. Actively controlled flaps are used to reduce vibrations, and noise levels and acoustic signatures are monitored throughout this process. Changes in the properties of the individual bladevortex interactions are related to the acoustic results. This paper represents the careful theoretical treatment of the combined helicopter noise and vibration problem using actively controlled flaps for vibration reduction.