Statistical analyses of a screen cylinder wake

The evolution of a screen cylinder wake was studied by analysing its statistical properties over a streamwise range of $x/d=10-60.$ The screen cylinder was made of a stainless steel screen mesh of 67% porosity. The experiments were conducted in a wind tunnel at a Reynolds number of $7000$ using an X-probe. The results were compared with those obtained in the wake generated by a solid cylinder. It was observed that the evolution of the statistics in the wake of the screen cylinder was different from that of a solid cylinder, reflecting the differences in the formation of the organized large-scale vortices in both wakes. The streamwise evolution of the Reynolds stresses, energy spectra and cross-correlation coefficients indicated that there exists a critical location that differentiates the screen cylinder wake into two regions over the measured streamwise range. The formation of the fully formed large-scale vortices was delayed until this critical location. Comparison with existing results for screen strips showed that although the near-wake characteristics and the vortex formation mechanism were similar between the two wake generators, variation in the Strouhal frequencies was observed and the self-preservation states were non-universal, reconfirming the dependence of a wake on its initial condition. (paper)