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Turbulent thermal convection in a rotating stratified fluid

Published online by Cambridge University Press:  24 September 2002

M. A. LEVY
Affiliation:
Environmental Fluid Dynamics Program, Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287-9809, USA
H. J. S. FERNANDO
Affiliation:
Environmental Fluid Dynamics Program, Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287-9809, USA

Abstract

Turbulent convection induced by heating the bottom boundary of a horizontally homogeneous, linearly (temperature) stratified, rotating fluid layer is studied using a series of laboratory experiments. It is shown that the growth of the convective mixed layer is dynamically affected by background rotation (or Coriolis forces) when the parameter R = (h2Ω3/q0)2/3 exceeds a critical value of Rc ≈ 275. Here h is the depth of the convective layer, Ω is the rate of rotation, and q0 is the buoyancy flux at the bottom boundary. At larger R, the buoyancy gradient in the mixed layer appears to scale as (db/dz)ml = 2, where C ≈ 0.02. Conversely, when R < Rc, the buoyancy gradient is independent of Ω and approaches that of the non-rotating case. The entrainment velocity, ue, for R > Rc was found to be dependent on Ω according to E = [Ri(1 + 2/N2)]−1, where E is the entrainment coefficient based on the convective velocity w∗ = (q0h)1/3, E = ue/w∗, Ri is the Richardson number Ri = N2h2/w2∗, and N is the buoyancy frequency of the overlying stratified layer. The results indicate that entrainment in this case is dominated by non-penetrative convection, although the convective plumes can penetrate the interface in the form of lenticular protrusions.

Type
Research Article
Copyright
© 2002 Cambridge University Press

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