Direct numerical simulations of noise generated by airfoil trailing edges

Direct numerical simulations (DNS) are conducted of flow past a NACA-0012 airfoil at various angles of attack. The aim is to directly compute both the near-field hydrodynamics and the far-field sound. The DNS data can then be used to investigate whether the approach of determining the noise radiation based on the surface pressure difference, as done in the classical trailing edge theory of Amiet, yields satisfactory results for finite thickness airfoils subject to mean loading effects. In addition, the accuracy of Amiet's surface pressure jump function is evaluated. Overall, the modified theory of Amiet appears to be suitable for finite thickness airfoils. However, Amiet's response function is not able to correctly predict the scattered pressure field for cases where large vortices pass the trailing edge. Moreover, predicting the airfoil self noise based only on the surface pressure difference appears not to be applicable for all frequencies at higher angles of attack because the radiated sound is only partly due to classical trailing edge noise mechanisms.

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