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Onset of stratification in a mixed layer subjected to a stabilizing buoyancy flux

Published online by Cambridge University Press:  26 April 2006

Y. Noh  and
H. J. S. Fernando
Y. Noh
Affiliation:
Department of Astronomy and Atmospheric Sciences, Yonsei University, Seoul 120-749, Korea
H. J. S. Fernando
Affiliation:
Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287-6106, USA
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Abstract

The formation of a thermocline in a water column, in which shear-free turbulence is generated both at the surface and bottom, and a stabilizing buoyancy flux is imposed at the surface, is studied using a laboratory experiment and a numerical model with the aim of understanding the formation of a tidal front in coastal seas. The results show that the formation of a thermocline, which always occurs in the absence of bottom mixing, is inhibited and the water column maintains a vertically mixed state, when bottom mixing becomes sufficiently strong. It is found from both experimental and numerical results that the criterion for the formation of a thermocline is determined by the balance between the rate of work that is necessary to maintain a mixed state against the formation of stratification by the buoyancy flux and the turbulent kinetic energy flux from the bottom supplied to the depth of thermocline formation. The depth of the thermocline, when it is formed, is found to decrease with bottom mixing.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 304 , 10 December 1995 , pp. 27 - 46
Copyright
© 1995 Cambridge University Press

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