Analysis of spurious sound due to vortical flow through permeable surfaces

Mao, Yijun; Hu, Zhiwei

doi:10.1016/j.ast.2019.105544

Cited by 12 publications

(2 citation statements)

References 49 publications

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“…1,2 Many feasible and efficient integral methods are available for noise prediction, these include the classical Ffowcs-Williams and Hawkings (FW-H) equation, 3,4 the Kirchhoff approach, 5,6 and the FW-H_pds (Ffowcs-Williams and Hawkings equation with permeable surface) equation. 7,8 Significant progress has been made in the development of these existing integral methods, and they are now widely used. In helicopters, strong blade-tip vortices are shed, and unsteady non-uniform downwash flowfield is induced by the motion of the rotor which affects the propagation of rotor noise.…”

Section: Introductionmentioning

confidence: 99%

Numerical study on the noise propagation characteristics of rotor in non-uniform downwash flowfield Based on Linearized Euler Equations

Yang

Chen

Zhao

et al. 2022

International Journal of Aeroacoustics

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To study the influence of non-uniform flowfield on the propagation characteristics of helicopter rotor noise, a Hybrid Computational Aeroacoustics (HCAA) method is developed. The acoustic source region is simulated by Computational Fluid Dynamics (CFD) technique with the Unsteady Reynolds Averaged Navier-Stokes equations (URANS) as the governing equations. Acoustic near-field is simulated by Computational Aeroacoustics (CAA) technique with the Linearized Euler Equations (LEE) as the governing equations, and the numerical discretization of the LEE is accomplished by Runge-Kutta Discontinuous Galerkin (RKDG) method. A novel acoustic source extraction method based on pressure and pressure gradient is proposed to accomplish the one-way CFD-CAA weak coupling. The HCAA method is validated through comparisons with noise experimental data of the UH-1H model rotor and the BO-105 model rotor. Based on the proposed HCAA method, the convection and refraction effects of rotor noise under different collective pitch angles are analyzed. The results show that the distortion effect of the rotor noise is most affected by the non-uniformly distributed downwash velocity field, resulting in an increment of acoustic energy below the rotor plane. The effect of non-uniformly distributed downwash velocity on noise propagation increases with the increase of the collective pitch angle. For the UH-1H model rotor, the maximum change of the sound pressure level is 0.8 dB (about 10% change of the effective sound pressure).

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Section: Introductionmentioning

confidence: 99%

Numerical study on the noise propagation characteristics of rotor in non-uniform downwash flowfield Based on Linearized Euler Equations

Yang

Chen

Zhao

et al. 2022

International Journal of Aeroacoustics

View full text Add to dashboard Cite

show abstract

“…The quadrupole term is usually ignored under the assumption that the monopole and dipole terms dominate the far-field sound in very low Mach numbers flows. However, recent research has suggested that ignoring the quadrupole sources may result in spurious sound even at relatively low Mach numbers [3,4].…”

Section: Introductionmentioning

confidence: 99%