scholarly journals On Geometrical Aspects of Interior Ocean Mixing

2014 ◽  
Vol 44 (8) ◽  
pp. 2164-2175 ◽  
Author(s):  
Trevor J. McDougall ◽  
Sjoerd Groeskamp ◽  
Stephen M. Griffies
Keyword(s):  
Turbulent Mixing ◽  
Diffusion Tensor ◽  
Three Dimensional ◽  
Small Scale ◽  
Theoretical Studies ◽  
Vertical Diffusion ◽  
Mixing Processes ◽  
Spatial Direction ◽  
Dimensional Diffusion ◽  
The Difference

Abstract The small-slope approximation to the full three-dimensional diffusion tensor of epineutral diffusion gives exactly the same tracer flux as the commonly used projected nonorthogonal diffusive flux of layered ocean models and of theoretical studies. The epineutral diffusion achieved by this small-slope approximation is not exactly in the direction of the correct epineutral tracer gradient. That is, the use of the small-slope approximation leads to a very small flux of tracer in a direction in which there is no epineutral gradient of tracer. For (the tracer) temperature or salinity, the difference between the correct epineutral gradient and the small-slope approximation to it is proportional to neutral helicity. The authors also make the point that small-scale turbulent mixing processes act to diffuse tracers isotropically (i.e., the same in each spatial direction) and hence it is strictly a misnomer to call this process “dianeutral diffusion” or “vertical diffusion.” This realization also has implications for the diffusion tensor.

scholarly journals Numerical simulation of mixing by Rayleigh–Taylor and Richtmyer–Meshkov instabilities

1994 ◽  
Vol 12 (4) ◽  
pp. 725-750 ◽  
Author(s):  
D.L. Youngs
Keyword(s):  
Numerical Simulation ◽  
Turbulence Model ◽  
Turbulent Mixing ◽  
Inertial Confinement Fusion ◽  
Three Dimensional ◽  
Small Scale ◽  
Inertial Confinement ◽  
Two Dimensional ◽  
Confinement Fusion ◽  
Icf Target

Rayleigh-Taylor (RT) and Richtmyer–Meshkov (RM) instabilities at the pusher–fuel interface in inertial confinement fusion (ICF) targets may significantly degrade thermonuclear burn. Present-day supercomputers may be used to understand the fundamental instability mechanisms and to model the effect of the ensuing mixing on the performance of the ICF target. Direct three-dimensional numerical simulation is used to investigate turbulent mixing due to RT and RM instability in simple situations. A two-dimensional turbulence model is used to assess the effect of small-scale turbulent mixing in the axisymmetric implosion of an idealized ICF target.

scholarly journals The Thinness of the Ocean in S–Θ–p Space and the Implications for Mean Diapycnal Advection

2007 ◽  
Vol 37 (6) ◽  
pp. 1714-1732 ◽  
Author(s):  
Trevor J. McDougall ◽  
David R. Jackett
Keyword(s):  
Dimensional Space ◽  
World Ocean ◽  
Three Dimensional ◽  
Small Scale ◽  
Lateral Motion ◽  
Hydrographic Data ◽  
Mixing Processes ◽  
The World ◽  
The Mean ◽  
Three Dimensional Space

Abstract It is shown that the ocean’s hydrography occupies little volume in the three-dimensional space defined by salinity–temperature–pressure (S–Θ–p), and the implications of this observation for the mean vertical transport across density surfaces are discussed. Although ocean data have frequently been analyzed in the two-dimensional temperature–salinity (S–Θ) diagram where casts of hydrographic data are often locally tight in S–Θ space, the relatively empty nature of the World Ocean in the three-dimensional S–Θ–p space seems not to have received attention. The World Ocean’s data lie close to a single surface in this three-dimensional space, and it is shown that this explains the known smallness of the ambiguity in defining neutral surfaces. The ill-defined nature of neutral surfaces means that lateral motion along neutral trajectories leads to mean vertical advection through density surfaces, even in the absence of small-scale mixing processes. The situation in which the ocean’s hydrography occupies a large volume in S–Θ–p space is also considered, and it is suggested that the consequent vertical diapycnal advection would be sufficiently large that the ocean would not be steady.

scholarly journals Three-dimensional diffusion tensor microimaging for anatomical characterization of the mouse brain

2010 ◽  
Vol 64 (1) ◽  
pp. 249-261 ◽  
Author(s):  
Manisha Aggarwal ◽  
Susumu Mori ◽  
Tomomi Shimogori ◽  
Seth Blackshaw ◽  
Jiangyang Zhang
Keyword(s):  
Mouse Brain ◽  
Diffusion Tensor ◽  
Three Dimensional ◽  
Dimensional Diffusion ◽  
Anatomical Characterization

scholarly journals Rapid measurement of three-dimensional diffusion tensor

2007 ◽  
Vol 126 (15) ◽  
pp. 154501 ◽  
Author(s):  
H. Cho ◽  
X.-H. Ren ◽  
E. E. Sigmund ◽  
Y.-Q. Song
Keyword(s):  
Diffusion Tensor ◽  
Three Dimensional ◽  
Rapid Measurement ◽  
Dimensional Diffusion

scholarly journals Physical and remineralization processes govern the cobalt distribution in the deep western Atlantic Ocean

2014 ◽  
Vol 11 (6) ◽  
pp. 1561-1580 ◽  
Author(s):  
G. Dulaquais ◽  
M. Boye ◽  
M. J. A. Rijkenberg ◽  
X. Carton
Keyword(s):  
Atlantic Ocean ◽  
Large Scale ◽  
Vertical Diffusion ◽  
Mixing Processes ◽  
Western Atlantic ◽  
Western Atlantic Ocean ◽  
Deep Waters ◽  
Bottom Waters ◽  
The Difference ◽  
High Concentrations

Abstract. The distributions of the bio-essential trace element dissolved cobalt (DCo) and the apparent particulate Co (PCo) are presented along the GEOTRACES-A02 deep section from 64° N to 50° S in the western Atlantic Ocean (longest section of international GEOTRACES marine environment program). PCo was determined as the difference between total cobalt (TCo, unfiltered samples) and DCo. DCo concentrations ranged from 14.7 pM to 94.3 pM, and PCo concentrations from undetectable values to 18.8 pM. The lowest DCo concentrations were observed in the subtropical domains, and the highest in the low-oxygenated Atlantic Central Waters (ACW), which appears to be the major reservoir of DCo in the western Atlantic. In the Antarctic Bottom Waters, the enrichment in DCo with aging of the water mass can be related to suspension and redissolution of bottom sediments a well as diffusion of DCo from abyssal sediments. Mixing and dilution of deep water masses, rather than scavenging of DCo onto settling particles, generated the meridional decrease of DCo along the southward large-scale circulation in the deep western Atlantic. Furthermore, the apparent scavenged profile of DCo observed in the deep waters likely resulted from the persistence of relatively high concentrations in intermediate waters and low DCo concentrations in underlaying bottom waters. We suggest that the 2010 Icelandic volcanic eruption could have been a source of DCo that could have been transported into the core of the Northeast Atlantic Deep Waters. At intermediate depths, the high concentrations of DCo recorded in the ACW linearly correlated with the apparent utilization of oxygen (AOU), indicating that remineralization of DCo could be significant (representing up to 37% of the DCo present). Furthermore, the preferential remineralization of phosphate (P) compared to Co in these low-oxygenated waters suggests a decoupling between the deep cycles of P and Co. The vertical diffusion of DCo from the ACW appears to be a significant source of DCo into the surface waters of the equatorial domain. Summarizing, the dilution due to mixing processes rather than scavenging of DCo and the above-mentioned remineralization could be the two major pathways controlling the cycling of DCo into the intermediate and deep western Atlantic.

scholarly journals Laser generated Richtmyer–Meshkov and Rayleigh–Taylor instabilities and nonlinear wave-vortex paradigm in turbulent mixing. II. Near-central region of Gaussian spot

2017 ◽  
Vol 35 (2) ◽  
pp. 210-225 ◽  
Author(s):  
Stjepan Lugomer
Keyword(s):  
Central Region ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Three Dimensional ◽  
Target Surface ◽  
Bubble Collapse ◽  
Small Scale ◽  
New Paradigm ◽  
Vortex Filaments ◽  
Coherent Wave

AbstractLaser-induced three-dimensional (3D) Richtmyer–Meshkov and Rayleigh–Taylor instabilities (RMI and RTI) on metal target in the semi-confined configuration (SCC) show the new paradigm of wave-vortex mixing. The SCC enables extended lifetime of a hot vapor/plasma plume above the target surface and the formation of fast multiple reshocks. This causes – in the central region (CR) of Gaussian-like spot – the evolution of RMI with the spike breakup (Lugomer, 2016b), while in the near CR causes the RMI followed by the RTI. The density interface is transformed into the large-scale broken irregular, quasi-periodic web, which comprises the RTI mushroom-shape spikes and the coherent wave-vortex structures such as the line solitons and vortex filaments. The intensity and direction of reshocks change (due to irregularity of the interface) and cause the formation of domains with the weak and the strong reshocks effects. The weak reshocks affect mushroom-shape spikes only slightly, while the strong ones cause their deformation and symmetry break, bubble collapse, and separation of the horizontal flow into vortex ribbons. Interaction of ribbons with spikes and bubbles causes the ribbon pinning, looping, winding, and formation of knotted and tangled structures. The line solitons, vortex filaments, and ribbons tend to organize into complex large-scale structures with the low wave-vortex turbulent mixing. They represent the new paradigm of 3D RMI and RTI in which the transition to the small-scale turbulent mixing does not appear.

Robust Volume-Based Approach for the Turbulent Mixing Efficiency

2005 ◽  
Vol 128 (4) ◽  
pp. 864-873 ◽  
Author(s):  
Roberto C. Aguirre ◽  
Haris J. Catrakis ◽  
Jennifer C. Nathman ◽  
Philip J. Garcia
Keyword(s):  
Turbulent Mixing ◽  
Mixture Fraction ◽  
Mixing Efficiency ◽  
Small Scale ◽  
Fluid Interfaces ◽  
Pure Fluid ◽  
Scale Sensitivity ◽  
The Difference ◽  
Mixed Fluid

This paper considers the mixture fraction which is often used to quantify the turbulent mixing efficiency in fluid engineering devices. We contrast a volume-based approach, where the mixture fraction is quantified directly using the volume bounded by the interface between mixed versus pure fluid, to a surface-based approach that requires area integrals of all mixed-fluid interfaces. Experimentally, we investigate the resolution-scale robustness of the volume-based approach compared to the small-scale sensitivity of the surface-based approach. The difference in robustness between these approaches has implications for examining, modeling, and optimizing the turbulent mixing efficiency.

Estuaries and coastal waters

1962 ◽  
Vol 265 (1322) ◽  
pp. 320-325 ◽  
Keyword(s):  
Turbulent Mixing ◽  
Coastal Waters ◽  
Basic Feature ◽  
Small Scale ◽  
Density Currents ◽  
Physical Processes ◽  
Mixing Processes ◽  
Salinity Water ◽  
Induced Currents ◽  
Upstream Flow

The basic feature of an estuarine circulation is a seaward flow of lower salinity water in the upper layer and an upstream flow of higher salinity below. The intensity of the circulation and its effect on the distribution of salinity and other properties of the water depend on the degree of turbulent mixing, which in turn is a function of the tidal currents. As an example of a study of the physical processes involved, a brief account is given of an investigation in the Mersey estuary. There is a similar tendency for density currents to be generated in coastal w aters, but there they are modified by geostrophic effects. Wind-induced currents assume a greater importance and often predominate, exerting a considerable influence on the mixing processes. Further progress in understanding the processes taking place in estuaries and coastal waters should be made by theoretical studies, by small-scale experiments and by carefully planned observations at sea.

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