Statistical geometry of subgrid-scale stresses determined from holographic particle image velocimetry measurements

Three-dimensional velocity distributions of a turbulent flow in the core region of a square duct at Re H = 1.2 x 10 5 are measured using holographic particle image velocimetry (HPIV). Spatial filtering of the 136 x 130 x 128 velocity vector maps enables calculation of subgrid-scale (SGS) stresses and parameters based on the filtered velocity gradients, such as the filtered strain-rate tensor and vorticity vector