Passive control of rotorcraft high-speed impulsive noise

[摘要] A strong, normal shock wave, terminating a local supersonic area located at the tip of a helicopter blade, not only limits the aerodynamic performance, but also constitutes an origin of the High-Speed Impulsive (HSI) noise. The application of a passive control device (a shallow cavity covered by a perforated plate) just beneath the interaction region weakens the compression level, thus reducing the main source of the HSI noise. The numerical investigation based on the URANS approach and Bohning/Doerffer (BD) transpiration law (SPARC code) confirms a large potential of the new method. Two exemplary implementations, adapted to model helicopter rotors tested at NASA Ames facility in transonic conditions: Caradonna-Tung (lifting, transonic hover) and Caradonna-Laub-Tung (non-lifting, high-speed forward flight), demonstrate the possible gains in terms of the reduction of acoustic pressure fluctuations in the near-field of the blade tip. The CFD results are validated against the experimental data obtained for the reference configurations (no control), while the analysis of the passive control arrangement is based on a purely numerical research. The normal shock wave is effectively eliminated by the wall ventilation exerting a positive impact on the generated level of the HSI noise.

[发布机构] Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, Gdask; 80-231, Poland^1

[效力级别] 力学 [学科分类] 力学，机械学

[关键词] Acoustic pressures;Aero-dynamic performance;High-speed impulsive noise;Interaction region;Normal shock waves;Numerical investigations;Passive control devices;Transonic conditions