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.