Iranian National Institute for Oceanography and Atmospheric Sciences (INIOAS)
Three-dimensional RANS simulations are employed numerically to study flow characteristics around a near-wall circular cylinder for varying gap-to-diameter (G/D) ratios (Where G is the gap between the cylinder and the wall and D is the cylinder diameter) and at Reynolds numbers from 100 to 3900. Pressure distribution around the circular cylinder, base pressure magnitude, separation and stagnation angles, force coefficients and Strouhal numbers were calculated and compared for all of the cases. Inception of vortex shedding can be seen when a sudden decrease in the maximum of positive pressure coefficient occurs. Vortex shedding mechanism and possibility of suppression further investigated via comparison of swirling strength in upper and lower vortex regions through parameter Λ, which signifies vortical activity and balance with respect to the wake center-line and also the flow type parameter, λ, representing the extensional strain dominance in the wake flow and gap flow. Vortex shedding suppression observed for the cases with the high unbalance vorticity content in the vortex regions, namely for Λ ≥ 2.