A comparative study on cross-buoyancy mixed convection around expanded and tapered trapezoidal bluff bodies

Abstract

Numerical computations have been realized to explore and evaluate the laminar mixed convection heat transfer from a heated trapezoidal bluff body. Two different configurations of the trapezoidal bluff body viz. expanded and tapered considered and a comparison has been made at different operational parameters. The spectrum of physical control parameters considered as Reynolds number (Re) = 10–50, Richardson number (Ri) = 0–1, and Prandtl number (Pr) = 0.7 (air). A finite volume method implemented on the collocated grid arrangement has been employed for numerical computations. Overall drag and lift coefficients are found higher for a tapered body as compared to an expanded body. However, average Nusselt number is greater for the expanded body as compared to the tapered one. With increase in Re at a given Ri, total drag coefficient is found to decrease in steady regime, but it increases in time-periodic regime. On increasing Ri, drag and lift coefficients decrease in the steady regime for both geometries. A correlation expressing the functional relationship of average Nusselt number with Re and Ri for both geometries has been proposed. Critical Re at Ri = 0.5 for the expanded geometry is found to be between Re = 46 and 47, while for the tapered body it exists between Re = 35 and 36. Maximum heat transfer enhancement for the tapered body with respect to the expanded body at Ri = 0, 0.5, and 1 is found to be approximately 26, 24, and 21%, respectively.

Keywords

Tapered bluff body expanded bluff body cross-buoyancy critical Reynolds number heat transfer enhancement

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