Computation and Extraction of Boundary Layer Parameters from Numerical Simulations for Use in Rotor Acoustics Models

Abstract

Low-order rotor broadband noise models require the boundary layer, displacement, and momentum thicknesses around the rotor's component airfoils to be provided. This data is often unavailable from prior literature, and may not be accurately computed (if at all) by simplified aerodynamics codes. To obtain the boundary layer thicknesses, this study builds on an integrated and robust meshing and solution approach using HAM2D, a Navier-Stokes computational code with advanced flow transition computations. This approach using HAM2D is already used to compute airfoil performance tables, and the computation of the boundary layer thicknesses imposes negligible additional overhead. The boundary layers computed by HAM2D are validated against prior data and wind tunnel PIV measurements conducted specifically for this study. In general, HAM2D shows good agreement with both experimental data sets, particularly with the PIV measurements conducted for this study, and where HAM2D diverges from historical data, so too do the PIV measurements. A few specific points of disagreement are noted, and future work will seek to reduce these inconsistencies.