Steady flow of power-law fluids past a slotted circular cylinder at low Reynolds number

Steady laminar flow past a slotted circular cylinder was investigated for non-Newtonian power-law fluids at the low Reynolds number (Re) range (5 <= Re <= 40). Flow simulation was carried out for shear-thinning fluids with their power-law indices (n) varying from 0.2 to 1 (n=0.2, 0.4, 0.6, 0.8, and 1). The normal (case A) and the slotted (case B) circular cylindrical geometries were considered, where the slit was placed between the front and the base pressure stagnation points. A finite volume method was used to calculate the flow field. The flow characteristics, such as flow separation angles, wake size, coefficients of pressure (C-p), and drag (C-D), were studied for different Re and n values. For all n values, the slotted cylinder effectively delayed the flow separation. It showed much better pressure recovery than the normal cylinder due to the interaction between the self-bleed from the slit exit to the cylinder wake. The vorticity of this bleed influenced the wake's vorticity, and an increase of 3%-26.4% in higher maximum surface vorticity was reported for the slotted cylinder. An increase of 0.7%-6.5% in the bubble length was observed for the normal cylinder due to early flow separation. An enhanced pressure recovery across the slotted cylinder resulted in a significant drop in the pressure drag with 0.2%-4.56% reduction in the overall drag coefficient.