Toward a Semi-Empirical Noise Prediction for Airfoils with Serrated Trailing Edges

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. A novel serrated trailing edge (STE) noise prediction model has been implemented and applied successfully to realistic airfoils with straight and serrated trailing edges. This model has several advantages over Howe's model as it utilizes an iterative procedure to solve the governing partial differential equations as opposed to the diffraction Green's function. The new model also takes both destructive and constructive interferences into account and is also applicable to high Mach numbers. Both the TNO and Chase wavenumber-frequency models have been implemented as input to the STE noise prediction model. The necessary boundary layer input parameters can be obtained from experiments or standard computational fluid dynamics simulations. In this work, we have used RANS CFD simulations to obtain the boundary layer information needed for the TNO and Chase models. Far-field noise comparisons are provided between the STE model and experimental data. A study to determine the most suitable location over the serration area to extract the boundary layer parameters has also been conducted and the changes in the flow due to the presence of the serrations are investigated. Differences in the predicted far-field sound reduction of up to 5 dB have been found for different boundary layer extraction locations over the serration area. The implemented STE model has the potential to improve the current noise prediction capabilities, and thereby improve serration design.