Non-Local Geometry of High Reynolds Number Wall-Bounded Turbulence using Tomographic Particle Image Velocimetry

Three-dimensional fields resulting from tomographic particle image velocimetry (Tomo-PIV) measurements in the buffer region of a fully developed flat plate turbulent boundary layer at Re$_{\theta} = 7800$ and 11800 are examined to extract statistics on the geometry and spatial distribution of large-scale coherent structures in wall bounded turbulence. Fields of $470^+ \times 70^+ \times 470^+$ and $920^+ \times 140^+ \times 920^+$ wall units are examined at a distance of $y^+ = 8$ to 55 and $y^+ = 15$ to 100 from the wall for Re$_{\theta} = 7800$ and 11800, respectively. Pattern recognition methods are used to extract and classify the structures. Results are compared with Stereo-PIV and direct numerical simulations of a boundary layer at Re$_{\theta} = 1950$. The enstrophy, dissipation and kinetic energy associated with each of these structures are considered.