Rotating Blade Trailing-Edge Noise: Experimental Validation of Analytical Model

This paper deals with the experimental validation of an analytical trailing-edge noise model dedicated to low-speed fans operating in free field. The model is intrinsically related to the aerodynamics of the blades and should lead to a useful fast-running tool to be included in a blade-design process in an industrial context. The investigations are made on a two-bladed low-speed axial fan without shroud, installed inside an anechoic room. The blades are instrumented with two sets of embedded small-size microphones (2.5 mm diam), and the wall-pressure signals are acquired via a slip ring mounted on the fan axis. The chord-based Reynolds number is about 200,000, and the tip Mach number about 0.07. The data base is completed by far-field measurements made with a single microphone on a moving support. The analytical model is based on a previously published extension of Amiet's trailing-edge noise theory. A blade is split into several strips in the spanwise direction, and the model is applied to each strip. For this the input data are interpolated from the measurements performed with the aforementioned sets of microphones. The trailing-edge noise model is more reliable for observer positions within ±30° from the fan-rotation plane.

[1]  Ahmed Naguib,et al.  Characterization of the Pressure Fluctuations Under a Fully Developed Turbulent Boundary Layer , 1998 .

[2]  Thomas F. Brooks,et al.  Effects of Angle of Attack and Velocity on Trailing Edge Noise , 2004 .

[3]  Michel Roger,et al.  Back-scattering correction and further extensions of amiet's trailing-edge noise model. Part 1: theory , 2005 .

[4]  J. Spurk.  Boundary Layer Theory , 2019, Fluid Mechanics.

[5]  Tom Hynes,et al.  Wall-Pressure Sources Near an Airfoil Trailing Edge Under Separated Laminar Boundary Layers , 2011 .

[6]  W. L. Keith,et al.  A Comparison of Turbulent Boundary Layer Wall-Pressure Spectra , 1992 .

[7]  Parviz Moin,et al.  The structure of wall-pressure fluctuations in turbulent boundary layers with adverse pressure gradient and separation , 1998, Journal of Fluid Mechanics.

[8]  R. K. Amiet,et al.  Noise of a model helicopter rotor due to ingestion of turbulence , 1979 .

[9]  G. Corcos.  Resolution of Pressure in Turbulence , 1963 .

[10]  Michel Roger,et al.  Competing Broadband Noise Mechanisms in Low-Speed Axial Fans , 2004 .

[11]  S. Moreau,et al.  Effect of Airfoil Aerodynamic Loading on Trailing Edge Noise Sources , 2005 .

[12]  F. Farassat,et al.  Broadband Trailing Edge Noise Predictions in the Time Domain. Revised , 2004 .

[13]  Michel Roger,et al.  Back-scattering correction and further extensions of Amiet's trailing-edge noise model. Part II: Application , 2009 .

[14]  Stéphane Moreau,et al.  Influence of turbulence modeling on airfoil unsteady simulations of broadband noise sources , 2005 .

[15]  Roger L. Simpson,et al.  Surface Pressure Fluctuations Beneath Two- and Three-Dimensional Turbulent Boundary Layers , 2000 .

[16]  M. S. Howe.  A review of the theory of trailing edge noise , 1978 .

[17]  J. Williams,et al.  Aerodynamic sound generation by turbulent flow in the vicinity of a scattering half plane , 1970, Journal of Fluid Mechanics.

[18]  Pierre Sagaut,et al.  Trailing-Edge Noise Prediction Using Large-Eddy Simulation and Acoustic Analogy , 2000 .

[19]  R. Amiet.  Noise due to turbulent flow past a trailing edge , 1976 .

[20]  Stefan Oerlemans,et al.  Aeroacoustic wind tunnel tests of wind turbine arfoils , 2004 .

[21]  P. Moin,et al.  Computation of Trailing-Edge Flow and Noise Using Large-Eddy Simulation , 2000 .

[22]  Patrick Rambaud,et al.  Numerical issues in the application of an amiet model for spanwise-varying incoming turbulence , 2008 .

[23]  S. Moreau,et al.  Validation of unstructured-mesh LES of the trailing-edge flow and noise of a Controlled-Diffusion airfoil , 2007 .

[24]  R. Amiet.  Acoustic radiation from an airfoil in a turbulent stream , 1975 .

[25]  Phillip Joseph,et al.  A frequency domain numerical method for airfoil broadband self-noise prediction , 2007 .

[26]  Thomas F. Brooks,et al.  Airfoil self-noise and prediction , 1989 .

[27]  B. McGrath,et al.  Some Features of Surface Pressure Fluctuations in Turbulent Boundary Layers With Zero and Favorable Pressure Gradients , 1987 .

[28]  G. Corcos.  The structure of the turbulent pressure field in boundary-layer flows , 1964, Journal of Fluid Mechanics.

[29]  Richard B. Gilchrist,et al.  Experimental Hydrophone‐Size Correction Factor for Boundary‐Layer Pressure Fluctuations , 1965 .

[30]  Scott C. Morris,et al.  The Effect of Blade Loading on Sound Sources in a Ducted Rotor , 2006 .

[31]  F. Fahy,et al.  Mechanics of flow-induced sound and vibration , 1989 .

[32]  Phillip Joseph,et al.  Frequency-Domain Method for Rotor Self-Noise Prediction , 2006 .

[33]  A. R. George,et al.  Trailing edge noise from hovering rotors , 1980 .

[34]  R. H. Schlinker,et al.  Helicopter rotor trailing edge noise , 1981 .

[35]  Phillip Joseph,et al.  Validity of Amiet's Model for Propeller Trailing-Edge Noise , 2011 .

[36]  Peter Bradshaw,et al.  ‘Inactive’ motion and pressure fluctuations in turbulent boundary layers , 1967, Journal of Fluid Mechanics.

[37]  T. Brooks,et al.  Trailing edge noise prediction from measured surface pressures , 1981 .

[38]  Michel Roger,et al.  Effect of Blade Design at Equal Loading on Broadband Noise , 2006 .

[39]  Michel Roger.  Rotating Blade Self Noise: Experimental Validation of Analytical Models , 2007 .

[40]  Michel Roger,et al.  Broadband Self Noise from Loaded Fan Blades , 2004 .

[41]  Howard P. Hodson,et al.  Experimental Investigation Into Trailing Edge Noise Sources , 2006 .