Control of turbulent coherent structures on flat panel by porous medium

Due to the unique internal structure of porous medium, the disturbance to the boundary layer involves both changing the dynamic behavior of the physical quantity in the conservation equation and changing the boundary conditions. In order to investigate the effect and mechanism of porous medium on the coherent structure near the wall of a flat panel, particle image velocimetry experiments of a flat panel and a flat panel with porous medium were carried out in a low turbulence return flow wind tunnel. The coherent structures of flat panel and porous medium-laden flat panel were compared in the study. The flow-normal plane flow display results show that porous medium can significantly lower the near-wall flow velocity, lift up the vortex structure in the near-wall region, reduce the vorticity, and effectively reduce the shear stress. Meanwhile, the velocity statistical quantities were extracted and fitted using the velocity profile method to show that at a wind velocity of 5.8 m/s and a porosity of 10 pores per inch (ppi), the maximum resistance reduction rate reaches 23.1%. The flow-spanwise plane flow display results show that the porous medium can destroy large-scale streak structures.