An experimental investigation on the near-field turbulence for an airfoil with trailing-edge serrations and an owl specimen

The ability to fly silently of most owl species has long been a source of inspiration for finding solutions for quieter aircraft and turbomachinery. This study concerns the mechanisms of the turbulence for an airfoil with trailing-edge serrations and a real owl specimen . the turbulence spatio-temporal information are measured with 3D hot-wire. The experiment is carried out in the Northwestern Polytechnical University low speed open jet wind tunnel on the SD2030 airfoil. Mach numbers range up to 0.3, with the Reynolds numbers from 1.9e+4 to 2.6e+5, the angle of attack α at −50, 00, and +50, the sawtooth of λ/h = 0.2. The individual trailing-edge serrations tips and valleys could be seen in the wake region. It is showed the spreading rate of the wake and the decay rate of the wake centerline velocity deficit increased with serrated edge compared to the straight edge. It is also found that the turbulence peak occurs further from the airfoil surface in the presence of the serrations, and the serrations generate additional horseshoe vortices shed in the near wake. However, the boundary layer statistics slightly upstream from the TE are not influenced by the serrations.