Pulsatile flow of power-law fluids over a sphere: Momentum and heat transfer characteristics

Abstract

The effect of pulsatile flow on the momentum and heat transfer characteristics for a sphere in power-law fluids is investigated numerically otherwise in the steady regime. Extensive results are presented in terms of streamlines, isotherms, pressure coefficient and local Nusselt number, drag coefficient and Nusselt number over the range of conditions as: Reynolds number (5 ≤ Re ≤ 120), Prandtl number (0.7 ≤ Pr ≤ 100), power-law index (0.3 ≤ n ≤ 1.5), frequency (π/4 ≤ ω* ≤ π) and amplitude of pulsations (0 ≤ A ≤ 0.8). The vortex grows during the deceleration phase of the pulsatile cycle and vice-versa. The pulsatile flow enhances heat transfer in shear-thinning fluids by 30% (at Re = 120, Pr = 100) over that of uniform flow conditions whereas the corresponding improvement is smaller than this value for shear-thickening fluids, i.e., n > 1. This is accompanied by a marginal increase in drag.