Study on the Unsteady Wakes Past a Square Cylinder near a Wall

Abstract

Experimental and numerical studies on the unsteady wake field behind a square cylinder near a wall were conducted to find out how the vortex shedding mechanism is correlated with a gap flow. The computations were performed by solving the unsteady 2-D Incompressible Reynolds Averaged Navier-Stokes equations with the ε-SST turbulence model, which was newly developed for more accurate prediction of large separated flows. Through the spectral analysis and the smoke wire flow visualization, it was found that velocity profiles in a gap region had strong influences on the formation of vortex shedding behind a square cylinder near a wall. From these results, Strouhal number distributions could be found, and the transition region of the Strouhal number was found at G/D=0.5~0.7 above the critical gap height. In that region, the primary and minor shedding frequencies were measured. The primary shedding frequency is affected by the interaction between the upper and the lower separated shear laye