Computational Aerodynamic and Aeroacoustic Analysis of Stalled Airfoil Sections

The scope of this study is to explore the applicability of a CFD-CAA framework employing a hybrid RANS/LES approach like Delayed Detached Eddy Simulations(DDES) for the flow field and the Ffowcs Williams and Hawkings (FW − H) analogy to obtain far-field noise predictions for the airfoil self-noise mechanism of separation-stall noise, in particular for the light and deep stall regimes. NACA0021 in deep stall and NACA 0012 under light stall are chosen for analysis. The surface pressure fluctuations from the numerical flow solution are propagated to the desired observer locations in the far-field with the help of the FW-H analogy. The far-field noise data is qualitatively compared with the available experimental data from previous studies. In both cases, good agreement was observed in the flow solution between the numerical results and experimental measurements. Far-field noise signatures for both the deep stall and light stall exhibited the same qualitative features as observed in experiments. Due to limitations and the difficulty in measuring stall noise, extensive validation was difficult, but salient features of far field noise reported in literature were captured by the numerical solution.