Airfoil Noise Reduction Using Flow Control in Blunt Trailing Edges

Walter Arias Ramirez¹; William Roberto Wolf¹

¹ University of Campinas

doi:10.20906/CPS/COB-2015-0179

Resumo

The aim of this study is to analyze the effects of suction and blowing on tonal noise generated by blunt trailing edges. Simulations are conducted for a NACA 0012 airfoil at different freestream Mach numbers and the angle of incidence is set equal to 0 deg. and 3 deg. Low to moderate Reynolds numbers are investigated in order to identify the physical mechanisms responsible for noise generation. At low Reynolds numbers, vortex shedding is the responsible for noise generation while at moderate Reynolds numbers, a feedback loop occurs due to wake instabilities. The effects of compressibility on sound generation and propagation are analyzed along with the effects of scattering by blunt trailing edges with four different radii of curvature. Sound generation is computed by a hybrid method and an accurate two-dimensional direct calculation. The hybrid approach uses direct calculation for near-field source computations and the Ffowcs Williams-Hawkings equation as the acoustic analogy formulation. Numerical results show that increasing the blowing effects at the trailing edge, one observes a reduction in amplitude of the dominant tonal peak. Furthermore, it is found that the the quadrupole sources move away from the airfoil surface, which also decreases noise scattering.

Palavras-chave: Airfoil Noise; Trailing Edge Bluntness; Acoustic Analogy; Flow Control; Direct Numerical Simulation