Flow structure in the downstream of square and circular cylinders

In this experimental work, a technique of digital particle image velocimetry (DPIV) is employed to characterize instantaneous vorticity and time-averaged velocity, vorticity, root mean square (rms) velocities, Reynolds stress correlations and phase-averaged contours in the downstream of circular, sharp-edged square and 45∘ orientated square cylinders in a uniform flow. Strouhal numbers for 550≤Re≤3400 are calculated from wake flow patterns. Shear layers surrounding the recirculation bubble region behind the cylinder are discussed in terms of flow physics and vortex formation lengths of large-scale Kármán vortices. Enhancement levels of Reynolds stress correlations associated with cross-stream velocity are clarified. Finally, flow structures depending on the cylinder geometry and Reynolds number are interpreted with quantitative representations.