Numerical simulation of flatback airfoil aerodynamic noise

•A hybrid approach is presented for the prediction of flatback airfoil noise.•The proposed method integrates the advantages of RANS and LES.•Flatback airfoil produces high vorticity flow near a blunt trailing edge.•Effects of the vortex shedding generate tonal noise at 150–200 Hz frequency ranges.•Hybrid LES/RANS model makes accurate predictions of the blunt trailing edge noise.

The present paper presents a possible path for developing a large eddy simulation (LES) applicable to high Reynolds-number complex turbulent flows and the performance of the coupling of LES with statistical turbulence models around the flow over a blunt trailing edge configuration. The turbulent fluctuations in the boundary layers at the inflow region of the LES domain are generated by a synthesized turbulence method. The hybrid RANS-LES model showed considerable improvement in prediction accuracy even at a moderate grid resolution. The aerodynamic comparison with experimental data shows like results for the pressure distributions surrounding a flatback airfoil. To predict accurately the noise radiation from the blunt trailing edge and to save computational costs, the near-field region is computed by embedded LES while the surrounding region is simultaneously computed by RANS. The Brooks, Pope, and Marcolini (BPM) semi-empirical model is used for noise comparison with the hybrid RANS-LES result and experimental data. The present hybrid RANS-LES method is found to be adequate for predicting aerodynamic noise generation by vortical flow in the vicinity of a blunt trailing edge airfoil over a range of frequencies.