An experimental investigation on coherent structures in near wall region of channel turbulent flow using DPIV
槽道湍流近壁结构的DPIV观测实验

The channel turbulence is studied experimentally by using a double frame straddling CCD camera DPIV system. Through the analysis of enormous data obtained from the experiment, the spatial structure and its evolution characteristics, together with the time history of turbulence in the near wall region, are obtained. The experimental result reveals that the phenomena such as ejection, sweep and variety of instantaneous velocity profiles of turbulence bear a direct physical relation with the evolution of the clockwise transverse vortex flowing downstream. The experimental result explains the form and the evolution of inflexion of the instantaneous velocity profile when the clockwise transverse vortex passes through it. From the experimental result, we can explain some characteristic mechanism of large scale structure. The experimental result also shows that DPIV system can provide quantitative and qualitative information concerning turbulence spatial characteristics and is suitable for experimental studies on turbulence in the near wall region.