Turbulence structure in a cylinder wake.

Large scale coherent structures in the fully turbulent wake of a circular cylinder in air were successfully educed up to the downstream distance of 40 d (d is the diameter of the cylinder) at a Reynolds number of 1.3 x 10 SUP 4. A newly developed conditional sampling technique, which is based on the recognition of spatially correlated vorticity, i.e. coherent vorticity from instantaneous vorticity maps was used. Topological features of the coherent structure and incoherent turbulence characteristics are documented; these suggest an important role of vortex stretching in the mechanisms of production and entrainment. Significant three dimension coherent structures were observed in the near wake region. (from authors' abstract)