MOMENTUM AND HEAT TRANSFER OF NON- NEWTONIAN FLUIDS AROUND A PAIR OF SQUARE CYLINDERS IN SIDE-BY-SIDE ARRANGEMENT

Abstract

In this study, the two-dimensional numerical investigation is conducted to analyse the steady and unsteady laminar flow and heat transfer characteristics for non-Newtonian fluid in a confined channel with two square cylinders of equal diameters arranged in side-by-side. The analysis is carried out for Reynolds number, Re = 1 — 40, power law index, n = 0.4 — 1 for a fixed Prandtl number, Pr = 50 for transverse separation ratio (i.e., gap ratio) of 2, 5 and 10 for the blockage ratio of 1/18. The engineering parameters such as total drag coefficient, average Nusselt number and Strouhal number, etc. are calculated for the above range of conditions. The flow and heat transfer remain steady for s/d = 2 for 1 < Re < 20 for 0.4 < n < 1 and for s/d = 5 for 1 < Re < 30 for 0.4 < n < 1, whereas unsteady periodic behavior is found for s/d = 2 for 30 < Re < 40 for 0.4 < n < 1 and for s/d = 5 for Re = 40 for 0.4 < n < 1. However, the flow and heat transfer are found to be steady for higher value of s/d = 10 for all Re and n. The effects of Reynolds number, power law index and gap ratio on the detailed kinematics of the flow and the heat transfer are presented. For a fixed value of power law index, it is observed that the value of the overall drag coefficient decreases with increasing Reynolds number, whereas the average Nusselt number for the square cylinders increases with increasing Reynolds number for a fixed value of separation ratio. The average Nusselt numbers are found higher for shear thinning fluids having lower value of power law index for fixed value of Reynolds number and separation ratio studied here and thus indicating higher heat transfer in shear thinning fluids than Newtonian fluids.