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

Abstract

ABSTRACTNumerical 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 < 0), the vortex shedding starts earlier on increasing 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 (CD) value reduces with the decrease in n, whereas the maximum CD 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 CD and the Colburn jh 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.