Pulsatile flow of power-law fluids over a heated cylinder: flow and heat transfer characteristics

Abstract

This study examines the momentum and heat transfer aspects of the laminar forced-convection induced by a pulsatile flow of power-law fluids past a heated circular cylinder by numerically solving the time-dependent momentum and energy equations over the ranges of dimensionless parameters as the cylinder Reynolds number based on the mean velocity (0.1 � Re � 40), Prandtl number (0.7 � Pr � 100), power-law index (0.3 � n � 1.4), frequency (0 � ω* � π) and amplitude (0 � A � 0.8). The detailed kinematics of the flow and temperature fields is visualized in terms of instantaneous streamlines and isotherm contours, especially adjacent to the cylinder. Further detailed insights are developed by examining the distribution of the pressure coefficient and local Nusselt number along the surface of the heated cylinder at different instants of time during the course of a periodic cycle. Finally, the overall gross characteristics are reported in terms of the time average drag coefficient and Nusselt number. It is possible to achieve varying levels of enhancement in the overall mixing of fluid and heat transfer under appropriate conditions of the amplitude of velocity, Reynolds number and power-law index. This is explained via the dynamics of the separated flow regions in terms of their growth and collapse during the course of a pulsation cycle. The fluid shear-thinning behavior promotes heat transfer in line with that seen in non-pulsating flows and shear-thickening behavior impedes it with reference to the corresponding value in Newtonian fluids otherwise under identical conditions.