Prediction of slat noise reduction measures using RANS based hybrid CAA method

The numerical prediction of broadband noise generated by the high-lift system using hybrid CAA methodology is discussed. A RANS based stochastic sound source modeling is applied by using the Stochastic Noise Generation and Radiation (SNGR) method. The SNGR method generates a synthetic pseudo-Turbulent unsteady velocity field, validated for homogeneous isotropic turbulence with the TKE spectrum. The convection effect of the stochastic velocity is reflected by solving the convection equation in SNGR method. The propagation of the sound field is computed by the Acoustic Perturbation Equations (APE) solver code in time-domain on multi-block structured grids. A high-order Dispersion Relation Preserving (DRP) finite difference scheme is applied. The hybrid method is performed on a three-element high-lift system for commercial aircraft to study and evaluate the noise mechanisms of slat flow. Different settings of slat noise reduction measures are considered and examined by simulation, including changing slat shape and injecting on slat. The results and effects of each noise reduction measures are discussed.