Data for double diffusers: Physical properties of aqueous salt-sugar solutions

Ruddick, Barry; Shirtcliffe, T. G. L.

doi:10.1016/0198-0149(79)90013-x

Cited by 70 publications

(49 citation statements)

References 4 publications

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“…Here γ is defined as ( ρ C – ρ 0 )/ ρ C , where ρ C is the density of particles (kg m −3 ). Δ ρ S is defined using the empirical polynomials in Ruddick and Shirtcliffe []. The characterization of the experiments was based on different density ratios of the two layers, defined as R ρ = Δ ρ S /Δ ρ C .…”

Section: Methodsmentioning

confidence: 99%

Enhanced sedimentation beneath particle‐laden flows in lakes and the ocean due to double‐diffusive convection

Jazi

Wells

2016

Geophysical Research Letters

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The transport rate of particles beneath sediment‐laden overflows and interflows in lakes and the ocean can be enhanced by double‐diffusive and settling‐driven convection. In previous experiments with sediment‐laden fluid overlaying a saline layer, visual measurements could only be made in the optically clear lower layer. Hence, there was difficulty distinguishing the two processes, hindering predictions of when enhanced sedimentation occurs. We used an Acoustic Doppler Velocimeter to measure velocities and turbulence above and below the initial sediment/salt interface. The velocity of the sediment fingers in the lower layer were always larger than the Stokes settling velocity of the particles, leading to an asymmetry in the flow field of the two convective layers. Sediment fingers only dominated when there were marginal density differences between the two layers. We conclude that double‐diffusive sediment fingers control sedimentation beneath interflows in most lakes, whereas settling‐driven convection is dominant in most oceanic overflows.

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Section: Methodsmentioning

confidence: 99%

Enhanced sedimentation beneath particle‐laden flows in lakes and the ocean due to double‐diffusive convection

Jazi

Wells

2016

Geophysical Research Letters

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“…The mean salinity of each height was converted to density by the relation from Ruddick and Shirtcliffe (1979) and the resulting vertical density profiles were used to obtain the depth of the interface h, and the average density of the upper layer 0,1 and of the lower layer Oa2" Since the~density gradient in the mixed layer was very small compared to the gradient at the interface, the representative layer density was chosen as the density at the mid-height of the layer. For the experiments with one screen rotating, 0~2 is constant with time and was measured prior to the experiment by a standard calibrated hydrometer.…”

Section: Experimental Set Up and Measurement Techniquesmentioning

confidence: 99%

Experiments on entrainment in an annulus with and without velocity gradient across the density interface

Chai

Kit

1991

Experiments in Fluids

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Abstract. The entrainment process in a two layer density stratified fluid column was studied experimentally by imposing external shear stress on one or both layers. The experiments have been conducted in an annular tank containing two water layers of different salt concentration and the shear stress was applied by means of rotating screens. The following quantities were measured: the screen velocity (which was kept constant during each experiment), the stress at the upper screen, and vertical profiles of circumferential velocity and density at different radial locations.When equal stress was imposed at the surface of the upper layer and at the bottom of the lower layer, entrainment took place from the two sides of the density interface at equal rate so that the interface was stationary in the central position between the two screens and there was no velocity gradient across the interface. The dependence of the entrainment coefficient on Richardson number obtained in these experiments was similar in form to that obtained in the shear-free experiments with an oscillating grid (e.g. Nokes 1988).When a shear stress was applied at the upper surface only, the upper layer depth increased with time and a velocity gradient existed at the interface. The influence of the interracial velocity gradient on the entrainment rate was studied by comparing the rates obtained with and without this velocity gradient. The entrainment rates were approximately the same for high values of the Richardson number while at low Richardson number the entrainment rate was much larger when a velocity gradient existed across the interface.The main results of this work are as follows: (i) Despite the curved geometry of the annular system, the dependence of the entrainment coefficient on Richardson number for shear-free interface experiments was found to be similar in form to that obtained for oscillating grid experiments.(ii) The entrainment across the interface is due to turbulent energy generated at some distance from the interface by an external source (i.e. shear stress induced by a screen) and due to turbulence produced locally at the interface by a velocity gradient. The relative contribution of each turbulence source to the total entrainment was found to depend on the stability of the interface.The numerous applications of turbulent mixing in nature and engineering, and the importance of this process from the basic point of view, have encouraged the research on turbulent mixing in stratified flows. Most of the studies have been performed in the laboratory as measurements in the field are more expensive and involve uncertainties arising from variations in the governing conditions. Although the scales of turbulence in the laboratory may be different from those in nature, the results obtained from such laboratory experiments have proved to be useful in understanding the basic mechanisms and even in predicting the growth rate of the mixed layer of the thermocline (e.g. Turner 1973).Previous laboratory experiments have been conducted primarily i...

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“…Finally solution 4 (the bottom layer) had a density of 1.065 g cm Ϫ3 with T 4 contributing 1.02 g cm Ϫ3 as in solutions 2 and 3. The appropriate quantities of salt and sugar necessary to create these solutions were determined from the tables in Ruddick and Shirtcliffe (1979). The solutions were allowed to sit overnight to achieve room temperature.…”

Section: Experimental Set-upmentioning

confidence: 99%

Diffusively-driven overturning of a stable density gradient

Thompson¹,

Veronis²

2005

J Mar Res

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We present the results of an experimental study on the formation and propagation of thermohaline intrusions from an initial state that is stably stratified in two diffusing components. The intrusions form in a layer that contains compensating horizontal gradients of the two components and that lies above a denser reservoir layer that is homogeneous. In the initial state, a vertical barrier separates the upper layer into two half layers each with a different concentration but with the same density. Differential diffusion of solute from the reservoir into the upper layer initiates intrusions that are separated by an interface and that move in opposite directions. The propagation of these intrusions is augmented by double-diffusive fluxes across the interface. Our experiments show that the formation of a diffusive interface between the two intrusions is a robust feature for all experiments that initially have a stable stratification in both diffusing components. A series of contrasting experiments with a fingering interface between the two intrusions was also performed using an initial density profile that favored fingering between part of the upper layer and the reservoir. A simple model is presented for intrusion propagation and density evolution in the intrusions, and the results are compared to measurements from the experiments. These experiments may help illuminate how thermohaline intrusions form in regions of the ocean where both temperature and salinity are stably stratified.

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Data for double diffusers: Physical properties of aqueous salt-sugar solutions

Cited by 70 publications

References 4 publications

Enhanced sedimentation beneath particle‐laden flows in lakes and the ocean due to double‐diffusive convection

Enhanced sedimentation beneath particle‐laden flows in lakes and the ocean due to double‐diffusive convection

Experiments on entrainment in an annulus with and without velocity gradient across the density interface

Diffusively-driven overturning of a stable density gradient

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