A Semi-empirical Wall Pressure Fluctuation Spectrum and Far-field Trailing-edge Noise Prediction Model
M. Kamruzzaman, D. Bekiropoulos, A. Wolf, Th. Lutz, W. Würz and E. Krämer, to be submitted to the International Journal of Aeroacoustics, 2012
A semi-empirical model of the wall pressure frequency spectrum beneath a two-dimensional, pressure gradient turbulent boundary-layer is presented based on the experimental wall pressure measurement date of various research groups. The measurements database includes both the equilibrium flat plate and non-equilibrium airfoil boundary-layer flow cases and cover a large range of Reynolds number. The enhanced model is a combination of the modified Chase-Howe, Goody and Rozenberg models, and is a simple function of the ratio of the pressure and timescales of the outer to inner boundary-layer. The key advantage of the present model is that it incorporates the Reynolds number, boundary-layer loadings as well as pressure gradient effects through an amplitude scaling function and timescale ratio, and compares well to experimental data. Spectral features of the detail measurement data and various scaling behavior of the wall pressure spectrum are elaborately investigated. A summary of the results on the applicability and limitation of the model for various test cases is discussed. The enhanced model is further applied to develop a complete turbulent boundary-layer trailing-edge interaction (TBL-TE) far-field noise prediction scheme for the acoustics airfoil design of wind turbine blades. Prediction results are compared with the various well established experimental data base and encouraging results are found.