Influence of Transient Flight Maneuvers on Rotor Wake Dynamics and Noise Radiation

This paper presents a study of three flight maneuvers using a rotorcraft aeroacoustics model: “pop-up,” “popdown,” and an arrested descent. A time-accurate freevortex rotor wake model and a maneuvering rotor noise prediction code were used to compute the noise. All rotorcraft motions and rigid body blade motions were included in the respective models. The wake geometry and its development is described. It is shown that the magnitude and directivity of the noise is strongly dependent on the rotor wake characteristics when blade-vortex interactions occur. In the transient arrested descent maneuver, the wake geometry becomes extremely complicated, and a significant increase in both nonimpulsive and impulsive noise is predicted.

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