Mixed convection from a hemisphere in Bingham plastic fluids

Abstract

In this work, mixed convection in a Bingham plastic fluid from a heated hemi-sphere has been investigated numerically in the so-called aiding buoyancy configuration. The results reported herein, spanning the following ranges of conditions: Reynolds number, 1⩽Re⩽100, Prandtl number, 1⩽Pr⩽100, Richardson number, 0⩽Ri⩽10 and Bingham number, 0⩽Bn⩽100, are used to describe the momentum and heat transfer characteristics of a hemi-sphere oriented with its curved surface towards the oncoming fluid stream. In particular, flow characteristics are analyzed in terms of the streamlines and the morphology of fluid-like/solid-like regions and the corresponding heat transfer characteristics are examined via isotherm contours, local Nusselt number and average Nusselt number values to delineate the role of each of these parameters. The flow separates itself from the hemi-sphere at a much lower Reynolds numbers as compared to that for a sphere due to the sudden loss of the rear surface. The average value of the Nusselt number is influenced by four non-dimensional parameters, namely, Reynolds number, Prandtl number, Bingham number and Richardson number. Finally, the present results have been consolidated using the Colburn j-factor for predicting the value of the average Nusselt number in a new application.