OPTICAL STUDIES OF MIXED LAYER DEVELOPMENT IN A DOUBLE-DIFFUSIVE, THERMOHALINE SYSTEM

1982 ◽  
Author(s):  
Frank P. Incropera ◽  
Raymond Viskanta
Keyword(s):  
Mixed Layer ◽  
Optical Studies ◽  
Layer Development ◽  
Double Diffusive

Correlation of Mixed Layer Growth in a Double-Diffusive, Salt-Stratified System Heated From Below

1986 ◽  
Vol 108 (1) ◽  
pp. 206-211 ◽  
Author(s):  
T. L. Bergman ◽  
F. P. Incropera ◽  
R. Viskanta
Keyword(s):  
Mathematical Model ◽  
Mixed Layer ◽  
Layer Growth ◽  
Published Data ◽  
Convective Velocity ◽  
Thermally Driven ◽  
Mixed Layers ◽  
Layer Development ◽  
Growth Correlations ◽  
Double Diffusive

Although many mixed layer growth correlations have been developed for stratified solutions which are eroded by mechanically driven mixed layers, little has been done to determine their applicability to solutions for which erosion is thermally driven. In this study entrainment rates have been determined from measurements of mixed layer growth in salt-stratified solutions heated from below. Entrainment data have been obtained for Richardson numbers in the range 80 < Ri < 1000, and when normalized with respect to the mixed layer convective velocity, the data are well correlated in terms of Ri−1. The correlation also agrees with published data obtained at larger and smaller Richardson numbers for both thermally and salt-stratified solutions heated from below. Predictions based on use of the correlation in a mathematical model of mixed layer development are in excellent agreement with measured mixed layer heights and temperatures.

Double-Diffusive Fluxes in a Salt Gradient Solar Pond

1988 ◽  
Vol 110 (1) ◽  
pp. 17-22 ◽  
Author(s):  
J. F. Atkinson ◽  
E. Eric Adams ◽  
D. R. F. Harleman
Keyword(s):  
Mixed Layer ◽  
Molecular Diffusion ◽  
Numerical Models ◽  
Mechanical Stirring ◽  
Solar Pond ◽  
Salt Gradient ◽  
Layer Region ◽  
Diffusive Fluxes ◽  
Effective Diffusivities ◽  
Double Diffusive

The possible influence of double-diffusive stratification on the vertical transport of salt and heat in a mixed-layer simulation model for a salt gradient solar pond is examined. The study is concerned primarily with the interfacial fluxes across the boundary between the gradient zone and upper convecting zone of solar ponds, though the arguments presented should be applicable to other “diffusive” interfaces as well. In the absence of mechanical stirring in the upper convecting zone (e.g., by wind), double diffusive instabilities could govern the vertical flux of heat and salt by adjusting interfacial gradients of temperature and salinity which control transport by molecular diffusion. Because these gradients are generally too sharp to be resolved by numerical models, the fluxes can either be modeled directly or be parameterized by grid-dependent “effective diffusivities.” It is shown that when mechanical stirring is present in the mixed layer, double-diffusive instabilities will not be allowed to grow in the interfacial boundary layer region. Thus, double-diffusive fluxes become important only in the absence of stirring and, in effect, provide a lower bound to the fluxes that would be expected across the interface.

Mixed Layer Development in a Salt-Stratified Solution Destabilized by a Discrete Heat Source

1987 ◽  
Vol 109 (3) ◽  
pp. 802-803 ◽  
Author(s):  
T. L. Bergman ◽  
A. Ungan ◽  
F. P. Incropera ◽  
R. Viskanta
Keyword(s):  
Heat Source ◽  
Mixed Layer ◽  
Discrete Heat Source ◽  
Layer Development

Interferometric study of stable salinity gradients heated from below or cooled from above

1982 ◽  
Vol 116 ◽  
pp. 411-430 ◽  
Author(s):  
W. T. Lewis ◽  
F. P. Incropera ◽  
R. Viskanta
Keyword(s):  
Mixed Layer ◽  
Mixing Layer ◽  
Density Distributions ◽  
Salinity Gradients ◽  
Isothermal Boundary ◽  
Secondary Layer ◽  
Constant Heating ◽  
Mixed Layers ◽  
Layer Development ◽  
Heating From Below

Mixing-layer development is investigated in laboratory experiments of salt-stratified solutions which are cooled from above or heated from below through the imposition of isothermal boundaries. A Mach-Zehnder interferometer is used to infer salt and density distributions within stable regions of the solution and to determine the extent of mixing-layer development. In both heating from below and cooling from above, this development differs significantly from that which has been observed for constant heating from below. Although the formation of a secondary mixed layer is observed, it does not lead to the development of additional mixed layers. Instead, the secondary layer eventually recedes, and the existence of a single mixed layer is restored. This behaviour is due to the isothermal boundary and the effect which it has no decreasing the heat transfer to or from the solution with increasing time. Once the condition of a single mixed layer is restored, extremely large (stable) density gradients develop in the boundary layer separating the mixed and stable regions, and subsequent growth of the mixed layer is slow. In cooling from above, mixing-layer development depends strongly on whether the isothermal boundary is in direct contact with the solution or separated by an air space.

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