Wall pressure spectra modelling for trailing edge noise in non-equilibrium adverse pressure gradient boundary layers.*

Based on existing direct numerical simulation (DNS) datasets of non-equilibrium boundary layers over flat plate or airfoils with and without separation, widely used semi-empirical wall-pressure-spectra models such as Goody’s, Rozenberg’s, and Lee’s models are tested. All tested models display large errors near region of strong adverse pressure gradients (APG) and in the region of separated flow, mainly due to the models’ direct dependences on local friction velocity as a parameter.

The datasets also suggest that the local maximum Reynolds stress appears to collapse well the wall pressure spectra in low frequency range and is thus considered the best scaling in this range. We explore modifications based on Rozenberg-Lee’s or Goody’s model. The goal is to remove excessive sensitivity to friction velocity in high APG regions and to integrate history effect of the pressure gradient, for example by including Coles’ parameter explicitly.

The new model will enable more accurate trailing edge noise prediction for cases with strong APG or separated boundary layers, such as flows around highly loaded or low Reynolds number airfoils.

 

Support from Trane Technologies, Carrier, and Ziehl-Abegg is acknowledged, under the Consortium of Ultra High-Efficiency and Quiet Fans.