Effects of shear-thinning nature and opposing buoyancy from a square geometry in a confined framework

Numerical computations were brought up to study the effect of opposing buoyancy mixed convection (Ri?=?0 to ??1) flow of power law shear-thinning fluids past a confined cooled square bluff body at Prandtl numbers (Pr)?=?1, 50 and Reynolds numbers (Re)?=?1–40. Irrespective of the n, Ri, Pr, and Re, the flow separation is delayed with increasing confinement (β). The vortex shedding and flow separation start earlier for shear-thinning fluids than Newtonian fluid. For opposing buoyancy (Ri?Pr (except for n?=?0.2, Ri?=??1). Also, the periodic unsteady transition appears at some higher value of Re on increasing Ri for fixed Pr. The drag coefficient (C_D) value reduces with the decrease in n, whereas the maximum C_D is noted for Newtonian fluids. The maximum augmentation in the heat transfer was reached about 9 and 36% on comparing with Newtonian fluids and forced convection case, respectively, and also the corresponding maximum compression in heat transfer was found about 15 and 5%, respectively. The numerical results have also been correlated for C_D and the Colburn j_h factor values for various Re, Pr, Ri, and n. In surplus, the effects of wall confinement ranging from β?=?25 to 50% on flow separation and engineering output parameters were studied in a steady regime.