Modification of Flow Structure and Sound Source by Hybrid Porous-serrated Trailing Edge

The effects of hybrid porous-serrated trailing edge on flow structure and sound source of NACA65(12)-10 at moderate Reynolds number (Rec = 5 × 105) have been investigated by Delayed Detached Eddy Simulation (DDES). Compared with conventional serrated trailing edge, the pressure fluctuation in the vicinity of hybrid porous-serrated trailing edge is further decreased significantly. The typical necklace vortex structures stretching across adjacent serrations are suppressed by the porous additive. It is found that porous media changes the shear stress distribution along the serration edge and inside the serration gap, which consequently eliminates the generation of necklace vortex. Therefore, the deformation of vortex tube caused by velocity vector is weakened. The underlying mechanisms associated to the sound source modification are analyzed based on vortex sound theory. The magnitude of Lamb vector and the angle between vorticity and velocity vectors are synchronously reduced by the porous additive, which implies that the present hybrid porous-serrated trailing edge has important influence on the further attenuation of far-field aerodynamic noise.