CH-46 rotor acoustics analysis: continued analysis of in-flight maneuvers

The breakdown of the linearized theory and the role of quadrupole sources in transonic rotor acoustics

Journal of Fluid Mechanics ◽

10.1017/s0022112091002537 ◽

1991 ◽

Vol 226 ◽

pp. 591-624 ◽

Cited By ~ 10

Author(s):

H. Ardavan

Keyword(s):

Green’S Function ◽

Green's Function ◽

Impulsive Noise ◽

Near Field ◽

Point Of View ◽

Rotating Frame ◽

Homogeneous Wave ◽

Linearized Theory ◽

Near Field Sound ◽

Rotor Acoustics

The retarded Green's function for the linearized version of the equation of the mixed type governing the potential flow around a rotating helicopter blade or a propeller (with no forward motion) is derived and is shown to constitute the unifying feature of the various existing approaches to rotor acoustics. This Green's function is then used to pinpoint the singularity predicted by the linearized theory of rotor acoustics which signals its experimentally confirmed breakdown in the transonic regime: the gradient of the near-field sound amplitude, associated with a linear flow which is steady in the blade-fixed rotating frame, diverges on the sonic cylinder at the dividing boundary between the subsonic and supersonic regions of the flow. Prom the point of view of the equivalent Cauchy problem for the homogeneous wave equation, this singularity is caused by the imposition of entirely non-characteristic initial data on a space—time hypersurface which, at its points of intersection with the sonic cylinder, is locally characteristic. It also emerges from the analysis presented that the acoustic discontinuities detected in the far zone are generated by the quadrupole source term in the Ffowcs Williams-Hawkings equation and that the impulsive noise resulting from these discontinuities would be removed if the flow in the transonic region were to be rendered unsteady (as viewed from the blade-fixed rotating frame).

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A five year review on DFVLR helicopter/rotor acoustics research

10.2514/6.1987-912 ◽

1987 ◽

Author(s):

H. HELLER ◽

W. SPLETTSTOESSER ◽

K.-J. SCHULTZ

Keyword(s):

Helicopter Rotor ◽

Rotor Acoustics

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Order tracking signal processing for open rotor acoustics

Journal of Sound and Vibration ◽

10.1016/j.jsv.2014.04.005 ◽

2014 ◽

Vol 333 (16) ◽

pp. 3818-3830 ◽

Cited By ~ 15

Author(s):

David B. Stephens ◽

Håvard Vold

Keyword(s):

Signal Processing ◽

Order Tracking ◽

Open Rotor ◽

Rotor Acoustics ◽

Tracking Signal

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Some results of the testing of a full-scale Ogee tip helicopter rotor; acoustics, loads, and performance

10.2514/6.1977-1340 ◽

1977 ◽

Cited By ~ 3

Author(s):

W. MANTAY ◽

P. SHIDLER ◽

R. CAMPBELL

Keyword(s):

Full Scale ◽

Helicopter Rotor ◽

And Performance ◽

Rotor Acoustics

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Research on Calculation Method for Acoustic Scattering of Helicopter Noise

Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University ◽

10.1051/jnwpu/20203861275 ◽

2020 ◽

Vol 38 (6) ◽

pp. 1275-1283

Author(s):

Feng Fan ◽

Yaxiong Cao ◽

Lusheng Jiang ◽

Yongfeng Lin

Keyword(s):

Calculation Method ◽

High Frequency ◽

Acoustic Scattering ◽

Cfd Analysis ◽

Main Rotor ◽

Analysis Model ◽

Scatter Field ◽

The Time Domain ◽

Helicopter Main Rotor ◽

Rotor Acoustics

A new calculation method of helicopter rotor/fuselage acoustic scattering is developed. Firstly, a CFD analysis model is developed to simulate flow field of the rotor, which is based on the motional embedded grid system and RANS equations, and provides aerodynamic data for rotor noise calculation. Then, FW-H equations are employed to calculate the aeroacoustic characteristics of isolated rotor, and G 1A formulas are applied to calculate the rotor acoustic gradient to provide boundary condition for acoustic scattering. Based on these, the time-domain equivalent source method is applied to calculate acoustic scatter field, and the total acoustic field that considered the fuselage scatter is superposed by isolated rotor acoustics and the scatter one. Finally, the numerical simulations of helicopter main-rotor/fuselage and tail-rotor/fuselage scatter effect are conducted by using the developed models. The results indicate that the helicopter fuselage has important scatter effect on the high frequency acoustics of main rotor and tail rotor, and the acoustic scatter effect become more obvious with the smaller space between the main rotor (tail rotor) and fuselage.

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Some Peculiarities of Helicopter Main Rotor Aeroacoustic for Far-Field Observer

EPJ Web of Conferences ◽

10.1051/epjconf/201921302048 ◽

2019 ◽

Vol 213 ◽

pp. 02048

Author(s):

Alexander Kusyumov ◽

Sergey Mikhailov ◽

Sergey Kusyumov ◽

Elena Romanova ◽

Georgios Barakos

Keyword(s):

Experimental Data ◽

Cfd Simulation ◽

Helicopter Rotor ◽

Test Case ◽

Far Field ◽

Main Rotor ◽

Blade Loading ◽

Rotor Noise ◽

Helicopter Main Rotor ◽

Rotor Acoustics

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.

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