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The mixing in a room by a localized finite-mass-flux source of buoyancy

Published online by Cambridge University Press:  05 November 2002

C. P. CAULFIELD  and
ANDREW W. WOODS
C. P. CAULFIELD
Affiliation:
Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0411, USA
ANDREW W. WOODS
Affiliation:
BP Institute for Multiphase Flows, University of Cambridge, Madingley Road, Cambridge CB3 OEZ, UK
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Abstract

The mixing produced by a turbulent buoyant plume with finite mass flux in a room is examined analytically and numerically. The entrainment of ambient fluid into the ascending buoyant plume leads to a return flow in the room which carries fluid downwards from the top of the room. The cycling of ambient fluid through the buoyant plume and the return flow causes the density to become uniform and gradually evolve towards that of the source fluid. As a result the buoyancy flux associated with the input fluid decreases and the plume motion becomes dominated by the source momentum flux. We develop an asymptotic model of the mixing using buoyant plume theory for a momentum-dominated flow. This provides an analytical description of the evolution of the density in the room which is in excellent accord with a full numerical simulation, and provides an improved description of the experimental filling-box data originally presented by Baines & Turner (1969).

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 471 , 25 November 2002 , pp. 33 - 50
Copyright
© 2002 Cambridge University Press

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