Abstract
Mathematical models for helicopter rotor acoustics are usually based on the Ffowcs Williams–Hawkings (FW–H) equation. The level of rotor noise is determined by geometry (thickness noise) of a flying vehicle and distributed blade loading (loading noise). Initially, the FW-H equation was obtained from Euler’s equations and does not depend on the viscosity of flow. In the present work the UH-1H helicopter is considered as a test case for numerical CFD simulation and comparison to experimental data.
Highlights
Modern research in rotor noise is based on Computational Aeroacoustics (CAA) and Computational Fluid Dynamics (CFD) to estimate the near-field noise of aircraft
The thickness noise is determined by the geometry of the rotor blade and the rotor frequency
To estimate the loading noise requires a CFD solution of the pressure distribution on the blade surface or on of a fictitious permeable surface: using a permeable surface approach is an alternative mathematical formulation that allows for taking into account the High Speed Impulsive (HSI) noise [4]
Summary
Modern research in rotor noise is based on Computational Aeroacoustics (CAA) and Computational Fluid Dynamics (CFD) to estimate the near-field noise of aircraft. The thickness noise is determined by the geometry of the rotor blade and the rotor frequency. Additional sources, including Blade Vortex Interaction (BVI) noise and High Speed Impulsive (HSI) noise dominate at specific flight regimes. To estimate the loading noise requires a CFD solution of the pressure distribution on the blade surface or on of a fictitious permeable surface: using a permeable surface approach is an alternative mathematical formulation that allows for taking into account the HSI noise [4]. As mentioned above the thickness noise level is determined by the rotor blade geometry and the rotor frequency. Estimation of the influence of the collective angle on the thickness noise level of a hovering rotor is considered, using the FW-H equation. The HMB solver of Glasgow University and ANSYS Fluent are used.The sound pressure level is estimated for different observation angles
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