In order to understand the turbulence vortex structure near a porous wall, based on the PIV experimental data, a vector field analysis, quadrant and quadranthole analyses of the Reynolds shear stress are performed. The investigated flow fields are turbulent channel flows whose bottom walls are made of porous media. The porous media used are three kinds of foamed ceramics which have almost the same porosity (approx 0.8) but different permeability. Those analyses confirm that the contribution of near-wall sweeps becomes the most dominant near the permeable wall whilst the ejections overtake them in the buffer region. The kinematic energy of the penetrating vortices into the porous wall by the stronger sweeps is considered to dissipate deeper inside the porous media. Then, the momentum of the outward fluid motions, which have been pushed out from the wall and contribute to forming ejections, becomes weaker as the increase of the wall permeability. These result in shortening cane-like longitudinal vortices and legs of hairpin vortices since vortex motions cannot be kept going with the weakened ejections. Consequently, longitudinal vortices hardly survive and transverse vortices, which used to be the vortex heads of hairpin vortices losing their legs, develop over permeable walls.
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