Effect of blockage on fluid flow past a square cylinder at low Reynolds numbers.

A channel confined flow around a bluff object is significantly different from its unconfined counterpart. A confined flow is presumably more stabilized due to the presence of the confinement. This causes a delay in the onset of flow separation and vortex shedding in comparison to the unconfined flow. While the above facts have been reported for the confined flow around a circular object in a channel, the same for a square object is infrequent. The present study focuses on the steady flow past a stationary square cylinder placed in a channel at low Reynolds numbers 1 ≤ Re ≤ 30 . The behavior of the flow is observed through numerical simulation for various channel confinements ( 0.01 ≤ B ≤ 0.9 , blockage ratio). The steady state laminar two-dimensional incompressible flow equations are solved using a finite volume based technique. An effort is made to find the separation critical Reynolds number at all blockages. It is observed that the separation critical Reynolds number increases with an increase in the blockage ratio. Unsteady flow characteristics at various blockages are also studied at Re = 100. In the unsteady regime, the frequency of vortex shedding increases with an increase in the blockage. [ABSTRACT FROM AUTHOR]