Heat transfer in rotating Rayleigh-Bénard convection with rough plates.

Joshi, P. and Rajaei, H. and Kunnen, R.P. and Clercx, H.J.H. (2017) Heat transfer in rotating Rayleigh-Bénard convection with rough plates. Journal of Fluid Mechanics, 830. ISSN 00221120

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Abstract

This experimental study focuses on the effect of horizontal boundaries withpyramid-shaped roughness elements on the heat transfer in rotating Rayleigh–Bénardconvection. It is shown that the Ekman pumping mechanism, which is responsible forthe heat transfer enhancement under rotation in the case of smooth top and bottomsurfaces, is unaffected by the roughness as long as the Ekman layer thicknessδEissignificantly larger than the roughness heightk. As the rotation rate increases, andthusδEdecreases, the roughness elements penetrate the radially inward flow in theinterior of the Ekman boundary layer that feeds the columnar Ekman vortices. Thisperturbation generates additional thermal disturbances which are found to increase theheat transfer efficiency even further. However, whenδE≈k, the Ekman boundary layeris strongly perturbed by the roughness elements and the Ekman pumping mechanismis suppressed. The results suggest that the Ekman pumping is re-established forδE�kas the faces of the pyramidal roughness elements then act locally as a slopingboundary on which an Ekman layer can be formed.

Item Type: Article
Subjects: AERONAUTICS > Aerodynamics
Depositing User: Mrs SK Pratibha
Date Deposited: 25 Feb 2020 14:21
Last Modified: 25 Feb 2020 14:21
URI: http://nal-ir.nal.res.in/id/eprint/13293

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