Stereoscopic particle image velocimetry investigation of three-dimensional characteristics of vortex structure in a turbulent channel flow

We investigate the three-dimensional characteristics of turbulence structures in a turbulent channel flow by employing stereoscopic particle image velocimetry (SPIV). The SPIV measurement was performed for a water flow at the Reynolds number Re = 1.1 x 10(4) in both the streamwise-spanwise (x-z) and spanwise-wall-normal (z-y) planes, respectively. A three-dimensional image of the vortex tubes or the hairpin vortex leg(s) inclined toward the wall was obtained. A series of wall-normal vortex cores were found to align with the low-speed streaks with opposite vorticity signals at both sides of the streaks in the x-z plane, which were cross-section slices of the inclined hairpin vortex leg(s).