Effect of Pitch Attitude on the Performance and Acoustics of a Lift-Offset Coaxial Rotor Based on High-Fidelity CFD/CSD Simulations
Zhongqi Jia, Seongkyu Lee, University of California Davis; Kalki Sharma, Kenneth Brentner, Pennsylvania State University
Effect of Pitch Attitude on the Performance and Acoustics of a Lift-Offset Coaxial Rotor Based on High-Fidelity CFD/CSD Simulations
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Effect of Pitch Attitude on the Performance and Acoustics of a Lift-Offset Coaxial Rotor Based on High-Fidelity CFD/CSD Simulations
Authors / Details: Zhongqi Jia, Seongkyu Lee, University of California Davis; Kalki Sharma, Kenneth Brentner, Pennsylvania State UniversityAbstract
This paper investigates the effect of pitch attitude on both performance and acoustics of a lift-offset coaxialrotor based on a first-principles and high-fidelity CFD/CSD loose coupling approach at 150 and 200 knots.The pitch attitudes selected for this research are -5 degrees, 0 degrees, and 5 degrees. The CFD/CSD loose coupling simulationsare carried out using the CREATE-AV software Helios while the coaxial rotor acoustics is simulated usingPSU-WOPWOP at eight microphones positioned below the lower rotor. A detailed aerodynamic analysis isperformed at 150 knots. A total of six major aerodynamic interactions are identified: 1) hub-wake interaction,2) self-BVI, 3) parallel rotor-to-rotor BVI, 4) blade-crossover events, 5) root-induced BVI, and 6) reversed-flowedge-vortex interactions. The strength of these interactions is dependent on the vehicle pitch attitude. The caseswith negative pitch attitude show significantly stronger impulsive pressure pulses, which is found to be inducedby parallel rotor-to-rotor BVIs of the lower rotor. Moreover, the positive and zero pitch attitude cases tend todominate the acoustic region on the starboard side of the coaxial rotor, whereas the negative pitch attitude caseshows higher acoustic pressure peaks on the port side. Overall, the case with a positive pitch attitude showssignificant improvement in rotor aerodynamic efficiency, rotor acoustics, and vehicle power performance athigh speed. The hemispherical acoustic simulation results at 150 knots also show that the noise is less likely topropagate in the forward direction with a positive pitch attitude.
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