Effects of non-uniform permeability on vortex shedding and noise control of blunt trailing edge

In this paper, the characteristics of the vortex shedding and noise of the blunt trailing edge with different porous permeable segment are studied by numerical simulation. The permeability distribution is adjusted through continuously changing the viscous drag of porous region to achieve uniformity and non-uniformity. The simulation results firstly show that the porous trailing edge can stabilize the free shear layer in a certain range of viscous drag coefficient to suppress the vortex shedding and reduce the overall noise level significantly. The optimized non-uniform permeability can further reduce the noise by 3dB than that of uniform permeability for porous blunt trailing edge. The discrete strip-shaped porous blunt trailing edge is proposed for more practical engineering application. It is found that the noise level is increased by 2 dB rather than optimal function distribution. However, the discrete strip porous trailing edge still has significant noise reduction capacity with respect to solid blunt trailing edge. The three-dimensional simulation demonstrates further that the non-uniform permeable trailing edge behaves more potential than uniform permeable trailing edge and reveals the crucial spanwise synergy effects by porous treatment.