scholarly journals The Effect of Wind on Salt Diffusion in a Stratified Flow at a River Mouth

1993 ◽  
Vol 37 ◽  
pp. 299-304
Author(s):  
Shizuo YOSHIDA ◽  
Morimasa OHTANI ◽  
Yoshio TASHIRO ◽  
Shuzo NISHIDA ◽  
Shirou YACI
Keyword(s):  
River Mouth ◽  
Stratified Flow ◽  
Salt Diffusion

On the lifetime of a pancake anticyclone in a rotating stratified flow

2016 ◽  
Vol 804 ◽  
pp. 688-711 ◽  
Author(s):  
Giulio Facchini ◽  
Michael Le Bars
Keyword(s):  
Time Evolution ◽  
Stratified Flow ◽  
Single Equation ◽  
Coriolis Parameter ◽  
Density Anomaly ◽  
Theoretical Predictions ◽  
Azimuthal Shear ◽  
Secondary Circulations ◽  
Pancake Vortex ◽  
Salt Diffusion

We present an experimental study of the time evolution of an isolated anticyclonic pancake vortex in a laboratory rotating stratified flow. Motivations come from the variety of compact anticyclones observed to form and persist for a strikingly long lifetime in geophysical and astrophysical settings combining rotation and stratification. We generate anticyclones by injecting a small amount of isodense fluid at the centre of a rotating tank filled with salty water linearly stratified in density. The velocity field is measured by particle image velocimetry in the vortex equatorial plane. Our two control parameters are the Coriolis parameter $f$ and the Brunt–Väisälä frequency $N$. We observe that anticyclones always slowly decay by viscous diffusion, spreading mainly in the horizontal direction irrespective of the initial aspect ratio. This behaviour is correctly explained by a linear analytical model in the limit of small Rossby and Ekman numbers, where density and velocity equations reduce to a single equation for the pressure. In particular for $N/f=1$, this equation ultimately simplifies to a radial diffusion equation, which admits an analytical self-similar solution. Direct numerical simulations further confirm the theoretical predictions that are not accessible to laboratory measurements. Notably, they show that the azimuthal shear stress generates secondary circulations, which advect the density anomaly: this mechanism is responsible for the slow time evolution, rather than the classical viscous dissipation of the azimuthal kinetic energy. The importance of density diffusivity is also analysed, showing that the product of the Schmidt and Burger numbers – rather than the bare Schmidt number – quantifies the importance of salt diffusion. Finally, a brief application to oceanic Meddies is considered.

Động lực phát triển vùng cửa Sông Hậu (cửa Định An - Tranh Đề)

2008 ◽  
Vol 30 (2) ◽  
pp. 130-135
Author(s):  
Hoa Mạnh Hùng ◽  
Nguyễn Quang Thành ◽  
Phan Thị Thanh Hằng
Keyword(s):  
River Estuary ◽  
River Mouth

Evaluating the dynamics of the Hau River estuary (Dinh An - Tranh De river mouth)

THE INITIAL RESULTS OF THE SUSPENDED SEDIMENT DYNAMICS DURING THE DRY SEASON IN THE HAU RIVER MOUTH AREA

2017 ◽  
Vol 17 (2) ◽  
Author(s):  
Nguyen Ngoc Tien ◽  
Dinh Van Uu ◽  
Nguyen Tho Sao ◽  
Do Huy Cuong ◽  
Nguyen Trung Thanh ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
River Mouth ◽  
Dry Season ◽  
Sediment Dynamics ◽  
Mouth Area ◽  
River Mouth Area ◽  
Initial Results

Microstructure determines water and salt permeation in commercial ion exchange membranes

2018 ◽  
Author(s):  
Ryan Kingsbury ◽  
Shan Zhu ◽  
Sophie Flotron ◽  
Orlando Coronell
Keyword(s):  
Energy Efficiency ◽  
Ion Exchange ◽  
Electrolyte Solutions ◽  
Polymer Chains ◽  
Salt Transport ◽  
Mixing Energy ◽  
Electrochemical Processes ◽  
Highly Correlated ◽  
Salt Diffusion ◽  
Exchange Membrane

Ion exchange membrane (IEM) performance in electrochemical processes such as fuel cells, redox flow batteries, or reverse electrodialysis (RED) is typically quantified through membrane selectivity and conductivity, which together determine the energy efficiency. However, water and co-ion transport (i.e., osmosis and salt diffusion / fuel crossover) also impact energy efficiency by allowing uncontrolled mixing of the electrolyte solutions to occur. For example, in RED with hypersaline water sources, uncontrolled mixing consumes 20-50% of the available mixing energy. Thus, in addition to high selectivity and high conductivity, it is desirable for IEMs to have low permeability to water and salt in order to minimize energy losses. Unfortunately, there is very little quantitative water and salt permeability information available for commercial IEMs, making it difficult to select the best membrane for a particular application. Accordingly, we measured the water and salt transport properties of 20 commercial IEMs and analyzed the relationships between permeability, diffusion and partitioning according to the solution-diffusion model. We found that water and salt permeance vary over several orders of magnitude among commercial IEMs, making some membranes better-suited than others to electrochemical processes that involve high salt concentrations and/or concentration gradients. Water and salt diffusion coefficients were found to be the principal factors contributing to the differences in permeance among commercial IEMs. We also observed that water and salt permeability were highly correlated to one another for all IEMs studied, regardless of polymer type or reinforcement. This finding suggests that transport of mobile salt in IEMs is governed by the microstructure of the membrane, and provides clear evidence that mobile salt does not interact strongly with polymer chains in highly-swollen IEMs. <br>

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