Research on drag reduction performance of turbulent boundary layer on bionic jet surface

Abstract

Based on the fact that jet formed in outer gill of sharks can reduce the wall friction during the breath process, a bionic jet surface model was established. The numerical simulations were carried out using shear stress transport k−ω model, and the simulation results accorded with that of experiments. First, in the case of fixed flow-velocity ratio, the drag reduction performance would be better with the smaller jet’s angle, and the impact that the angle has on the drag reduction would be greater with the increase in jet hole’s aperture. Second, in the case of fixed jet’s angle, the drag reduction had a nearly linear relationship with flow–velocity ratio. Namely, the drag reduction would be better as the flow–velocity ratio increased, and the larger the jet hole’s aperture, the better the drag reduction. In addition, compared with the case of smoothing surface, the flow structure in turbulent boundary layer was changed by jet, increasing the thickness of viscous bottom layer and decreasing the gradient of normal velocity perpendicular to wall. Finally, the drag reduction mechanism was proposed based on the increased velocity effect of turbulent core, isolation effect of wall and the increased turbulent damping effect.