Computation Of Wall-Pressure Spectra From Steady Flow Data For Noise Prediction

A method is proposed to calculate the trailing-edge broadband noise emitted from an airfoil, based on a steady Reynolds-averaged Navier Stokes solution of the flowfield. For this purpose, the pressure spectrum on the airfoil surface near the trailing edge is calculated using a statistical model from the Reynolds-averaged Navier Stokes mean velocity and turbulence data in the airfoil boundary layer. The obtained wall-pressure spectrum is used to compute the radiated sound by means of an aeroacoustic analogy, namely, A inlet's theory of airfoil sound. The statistical model for wall-pressure fluctuations is validated with two test cases front the literature, a boundary layer with an adverse pressure gradient, and a flat plate boundary layer without a pressure gradient. The influence of specific model assumptions is studied, such as the convection velocity of pressure-producing structures and the scale anisotropy of boundary-layer turbulence. Furthermore, the influence of the Reynolds-averaged Navier Stokes simulation on the calculated spectra is investigated using three different turbulence models. The method is finally applied to the case of a Video controlled-diffusion airfoil placed in a jet wind tunnel in the anechoic facility of Ecole Centrale de Lyon. Reynolds-averaged Navier Stokes solutions for this test case are computed with different turbulence models, the wall-pressure spectrum near the trailing edge is calculated using the statistical model, and the radiated noise is computed with Amiet's theory. All intermediate results of the method are compared with experimental data.