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Experiments on a plume with off-source heating: Implications for cloud fluid dynamics

Venkatakrishnan, L and Bhat, GS and Narasimha, R (1999) Experiments on a plume with off-source heating: Implications for cloud fluid dynamics. In: Journal Of Geophysical Research-Atmospheres, 104 (D12). pp. 14271-14281.

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Official URL: http://www.agu.org/pubs/crossref/1999/1999JD900034...

Abstract

We report here on a series of laboratory experiments on plumes, undertaken with the object of simulating the effect of the heat release that occurs in clouds on condensation of water vapor. The experimental technique used for this purpose relies on ohmic heating generated in an electrically conducting plume fluid subjected to a suitable alternating voltage across specified axial stations in the plume flow [Bhat et al., 1989]. The present series of experiments achieves a value of the Richardson number that is toward the lower end of the range that characteristics cumulus clouds. It is found that the buoyancy enhancement due to heating disrupts the eddy structures in the flow and reduces the dilution owing to entrainment of ambient fluid that would otherwise have occurred in the central region of the plume. Heating also reduces the spread rate of the plume, but as it accelerates the flow as well, the overall specific mass flux in the plume does not show a very significant change at the heat input employed in the experiment. However, there is some indication that the entrainment rate (proportional to the streamwise derivative of the mass flux) is slightly higher immediately after heat injection and slightly lower farther downstream. The measurements support a previous proposal for a cloud scenario [Bhat and Narasimha, 1996] and demonstrate how fresh insights into certain aspects of the fluid dynamics of clouds may be derived from the experimental techniques employed here.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Geophysical Union.
Department/Centre: Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited: 19 Jul 2009 05:46
Last Modified: 19 Jul 2009 05:46
URI: http://eprints.iisc.ernet.in/id/eprint/19331

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