Into the Physics of Rotor Aeroacoustics - Highlights of recent European Helicopter Noise Research

Abstract

Significant advances in understanding and controlling helicopter noise have been made in the course of several major European dedicated rotor aeroacoustics research projects over the past five, or so, years. The availability of the German Dutch Wind Tunnel (DNW), in particular, has enabled research on relatively large main rotor models (up to typically 40% full-scale). Here, the simultaneous application and use of blade-mounted absolute pressure sensors to probe into the very aeroacoustic source mechanisms, of advanced aoustic data acquisition systems for the radiated noise, of sophisticated flow visualisation and flow measurement techniques (such as the Laser Light Sheet and the Laser Doppler Velocimetry techniques) as well as of the Projected Grid method (a simplified Moir technique) to study the complex interrelationship of rotor aerodynamics and blade dynamic response, has provided much insight into the physics of rotor aeroaoustics. In an effort towards.