Double-diffusive interleaving due to horizontal gradients

1983 ◽  
Vol 137 ◽  
pp. 347-362 ◽  
Author(s):  
Judith Y. Holyer
Keyword(s):  
Stability Analysis ◽  
Small Region ◽  
Two Dimensional ◽  
Fully Nonlinear Equations ◽  
Salinity Stratification ◽  
Horizontal Gradients ◽  
Salinity Gradients ◽  
Horizontal Density Gradient ◽  
Double Diffusive ◽  
Vertical Gradients

In this paper we present a linear stability analysis for an unbounded, vertically stratified fluid which has compensating horizontal temperature and salinity gradients, so there is no horizontal density gradient. We obtain the most unstable perturbation for given linear horizontal and vertical gradients and calculate the growth rates, the vertical lengthscale of the intrusion and the slope of the intrusion to the horizontal. We show that the system is most unstable to two-dimensional disturbances and that, except for a small region in which the temperature stratification is unstable and the salinity stratification is stable, the most-unstable disturbance is non-oscillatory. We also obtain a solution to the fully nonlinear equations and calculate the fluxes of heat and salt. The nonlinear solution shows that alternating interfaces of salt-finger and diffusive interfaces will eventually appear on the intrusion when the vertical stratifications are both stable.

Two-dimensional effects in double-diffusive convection

1974 ◽  
Vol 63 (3) ◽  
pp. 577-592 ◽  
Author(s):  
J. S. Turner ◽  
C. F. Chen
Keyword(s):  
Two Dimensional ◽  
Double Diffusive Convection ◽  
Mechanism Of Formation ◽  
Concentration Gradients ◽  
One Dimensional ◽  
Horizontal Gradients ◽  
Diffusive Convection ◽  
Similar Density ◽  
Double Diffusive ◽  
Vertical Gradients

The limitations of existing one-dimensional experiments on double-diffusive convection are discussed, and a variety of new two-dimensional phenomena are described. We have used the sugar-salt system and shadowgraph photography to make exploratory studies of motions which can arise in a fluid with two smooth, opposing, vertical concentration gradients, with and without horizontal gradients. Many different effects have been observed, the most important of which are the following, (a) In the ‘finger’ case, local disturbances can propagate rapidly as wave motions, which cause a simultaneous breakdown to convection over large horizontal distances. (b) Layers formed in the’ diffusive’ sense overturn locally to produce fingers, but propagate more slowly, as convective rather than wave motions, (c) A series of layers, separated by diffusive interfaces, can become unstable, in the sense that successive layers merge in time as their densities become equal, (d) The presence of horizontally separated sources of water of similar density but differentT,Scharacteristics can lead to the development of strong vertical gradients and extensive quasi-horizontal layering.Most of our results are qualitative, but it is hoped that they will stimulate further quantitive work on each of the new processes described. It is already clear that much more needs to be done before the mechanism of formation of layers observed in the ocean can be regarded as properly understood.

Three-dimensional instabilities of steady double-diffusive interleaving

2000 ◽  
Vol 418 ◽  
pp. 297-312 ◽  
Author(s):  
OLIVER S. KERR
Keyword(s):  
Stability Analysis ◽  
Dimensional Stability ◽  
Three Dimensional ◽  
Finite Amplitude ◽  
Secondary Instability ◽  
Two Dimensional ◽  
Salinity Gradients ◽  
Secondary Instabilities ◽  
Double Diffusive

A stratified body of fluid with compensating horizontal temperature and salinity gradients can undergo an interleaving instability which takes the form of almost horizontal intrusions. As the amplitude of these intrusions grows they can undergo secondary instabilities which eventually leads to the mixing of the fluid in the interior of the intrusions. A previous study of the secondary instabilities focused on two-dimensional disturbances. These corresponded to experimental observations of that time which all seemed to indicate that flows were indeed two-dimensional. Some more recent experiments have shown that the initial secondary instability can make the flow three-dimensional, with the secondary instabilities taking the form of rolls with their axes aligned with the direction of the flow in the intrusions. Here we present a three dimensional stability analysis of steady finite-amplitude intrusions and look at the circumstances which can lead to the three-dimensional instabilities being more likely to be observed.

scholarly journals Thermohaline interleaving induced by horizontal temperature and salinity gradients from above

2021 ◽  
Vol 927 ◽  
Author(s):  
Junyi Li ◽  
Yantao Yang
Keyword(s):  
Scaling Laws ◽  
Fluid Layer ◽  
Horizontal Gradients ◽  
Density Anomaly ◽  
Salinity Gradients ◽  
Vertical Fluxes ◽  
Diffusive Convection ◽  
Different Types ◽  
Thermohaline Intrusions ◽  
Double Diffusive

In this work we show that horizontal gradients of temperature and salinity with compensating effects on density can drive thermohaline intrusion in the fluid layer below. Specifically, different types of double diffusive convection generate differential vertical fluxes from the top boundary, which then sustain horizontal temperature and salinity gradients within the bulk. Interleaving layers develop in the bulk and slope downward towards the cold fresh side, which are of the diffusive type. New layers emerge near the bottom boundary and shift the existing layers upward due to the density difference induced by the divergence of the vertical fluxes through the top surface. Detailed analyses reveal that the present intrusion is consistent with those in the narrow fronts, and both layer thickness and current velocity follow the corresponding scaling laws. Such intrusion process provides an extra path to transfer heat and salinity horizontally towards the cold and fresh side, but transfer the density anomaly towards the warm and salty side. These findings extend the circumstances where thermohaline intrusions may be observed.

Lamellar Porous Vermiculite Membranes for Boosting Nanofluidic Osmotic Energy Conversion

2021 ◽  
Author(s):  
Li Cao ◽  
Hong Wu ◽  
Chunyang Fan ◽  
Zhiming Zhang ◽  
Benbing Shi ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Power Density ◽  
Great Promise ◽  
Two Dimensional ◽  
Nanofluidic Channels ◽  
Salinity Gradients ◽  
Transmembrane Resistance

Lamellar membranes with two-dimensional nanofluidic channels hold great promise in harvesting osmotic energy from salinity gradients. However, the power density is often limited by the high transmembrane resistance primarily caused...

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