Study of Active Rotor Control for In-Plane Rotor Noise Reduction

In this paper, first a methodology to find a loading solution (of point control force) that results in noise reduction at a single observer is developed. A governing equation is established and the loading solution is obtained by solving the equation numerically. Here, the loading solution is the component of loading vector in radiation direction. The loading solution can provide complete noise cancellation at the target observer. Additionally, two methodologies to find a loading solution that results in noise reduction over a broad area are developed, which are combination methodology and prescribed formula methodology. Both chordwise and spanwise control forces are considered. The chordwise force solutions can provide over 6 dB reduction over a 60 deg azimuth range and a 100 deg elevation range. The spanwise force can provide over 6 dB reduction over a 100 deg azimuth range and a 60 deg elevation range. However, noise at some observers outside the target area is increased. Finally, two active devices are proposed. An active flap is studied to generate chordwise force, while a rotating winglet is studied to generate spanwise force to reduce noise.