Generic Airfoil Trailing-Edge Noise Prediction using Stochastic Sound Sources from Synthetic Turbulence

Abstract

A Computational Aeroacoustic (CAA) study is conducted for the simulation of broad- band trailing-edge noise radiated from a NACA0012 airfoil and a cambered non-symmetrical DU96 airfoil for different ow conditions. The chosen simulation approach uses a Reynolds Averaged Navier-Stokes (RANS) solution to describe the turbulence around the airfoil. With a stochastic method time resolved synthetic turbulence uctuations are derived which then describe the unsteady sound sources used for acoustic perturbation equations (APE). The simulated broadband noise spectra are evaluated for different sets of input parameters to determine the sensitivity of the used method towards these parameters. Calculated values are compared to available measurement data to validate the underlying assumptions and to give advices on the best practice settings. It is essential for any proper realization of sound sources from a stochastic method that the RANS turbulence statistics are accurately realized. A length scale smoothing procedure is presented which remedies the problem of spurious peaks in the realized turbulence statistics. A study is pursued regarding the tur- bulent energy spectra realized by the stochastic turbulence reconstruction. Two different spectra (Gauss and Liepmann) are analyzed. A positive effect of higher energy levels of the Liepmann spectrum in certain frequency ranges on the simulated sound field can be shown.