A gravity current model of cooling mantle plume heads with temperature-dependent buoyancy and viscosity

1996 ◽  
Vol 101 (B2) ◽  
pp. 3291-3309 ◽  
Author(s):  
David Bercovici ◽  
Jian Lin
Keyword(s):  
Mantle Plume ◽  
Current Model ◽  
Gravity Current ◽  
Temperature Dependent

A Temperature-dependent Current Model for Phemt on Gaas

2008 ◽  
Vol 22 (1) ◽  
pp. 39-46 ◽  
Author(s):  
L. Wang ◽  
R. M. Xu ◽  
Y. C. Guo ◽  
B. Yan
Keyword(s):  
Current Model ◽  
Temperature Dependent

A bottom gravity current model for CO2-enriched seawater

1993 ◽  
Vol 34 (9-11) ◽  
pp. 1065-1072 ◽  
Author(s):  
Helge Drange ◽  
Guttorm Alendal ◽  
Peter M. Haugan
Keyword(s):  
Current Model ◽  
Gravity Current

Voltage- and temperature-dependent gate capacitance and current model: application to ZrO/sub 2/ n-channel MOS capacitor

2002 ◽  
Vol 49 (11) ◽  
pp. 1969-1978 ◽  
Author(s):  
Yang-Yu Fan ◽  
R.E. Nieh ◽  
J.C. Lee ◽  
G. Lucovsky ◽  
G.A. Brown ◽  
...  
Keyword(s):  
Current Model ◽  
Temperature Dependent ◽  
Model Application ◽  
Mos Capacitor ◽  
Gate Capacitance

Two-phase gravity currents in porous media

2011 ◽  
Vol 678 ◽  
pp. 248-270 ◽  
Author(s):  
MADELEINE J. GOLDING ◽  
JEROME A. NEUFELD ◽  
MARC A. HESSE ◽  
HERBERT E. HUPPERT
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Fluid Flow ◽  
Current Model ◽  
Gravity Current ◽  
Capillary Forces ◽  
Gravity Currents ◽  
Flow In Porous Media ◽  
Two Phase ◽  
Residual Trapping

We develop a model describing the buoyancy-driven propagation of two-phase gravity currents, motivated by problems in groundwater hydrology and geological storage of carbon dioxide (CO2). In these settings, fluid invades a porous medium saturated with an immiscible second fluid of different density and viscosity. The action of capillary forces in the porous medium results in spatial variations of the saturation of the two fluids. Here, we consider the propagation of fluid in a semi-infinite porous medium across a horizontal, impermeable boundary. In such systems, once the aspect ratio is large, fluid flow is mainly horizontal and the local saturation is determined by the vertical balance between capillary and gravitational forces. Gradients in the hydrostatic pressure along the current drive fluid flow in proportion to the saturation-dependent relative permeabilities, thus determining the shape and dynamics of two-phase currents. The resulting two-phase gravity current model is attractive because the formalism captures the essential macroscopic physics of multiphase flow in porous media. Residual trapping of CO2 by capillary forces is one of the key mechanisms that can permanently immobilize CO2 in the societally important example of geological CO2 sequestration. The magnitude of residual trapping is set by the areal extent and saturation distribution within the current, both of which are predicted by the two-phase gravity current model. Hence the magnitude of residual trapping during the post-injection buoyant rise of CO2 can be estimated quantitatively. We show that residual trapping increases in the presence of a capillary fringe, despite the decrease in average saturation.

Buoyant flow of through and around a semi-permeable layer of finite extent

2016 ◽  
Vol 809 ◽  
pp. 553-584 ◽  
Author(s):  
Tri Dat Ngo ◽  
Emmanuel Mouche ◽  
Pascal Audigane
Keyword(s):  
Capillary Pressure ◽  
Graphical Representation ◽  
Current Model ◽  
Gravity Current ◽  
Two Dimensions ◽  
Total Flux ◽  
Vertical Column ◽  
Fine Grid ◽  
Permeable Layer ◽  
Counter Current

The buoyancy- and capillary-driven counter-current flow of $\text{CO}_{2}$ and brine through and around a semi-permeable layer is studied both numerically and theoretically. The continuities of the capillary pressure and the total flux at the interface between the permeable matrix and layer control the $\text{CO}_{2}$ saturation discontinuity at the interface and the balance between the buoyant and capillary diffusion fluxes on each side of the interface. This interface process is first studied in a one-dimensional (1-D) vertical column geometry using the concept of extended capillary pressure and a graphical representation of the continuity conditions in the ($S_{L}$, $S_{U}$) plane, where $S_{L}$ and $S_{U}$ are the lower and upper saturation traces at the interface, respectively. In two dimensions, we heuristically extend the two-phase gravity current model to the case where the current is bounded by a semi-permeable layer. Consequently, the current is not saturated with $\text{CO}_{2}$, and its saturation and shape are derived from the flux and capillary pressure continuity conditions at the interface. This simplified model, which depends on $\text{CO}_{2}$ saturation only, is compared to fine grid simulations in the capillary-free and gravity-dominant cases. A good agreement is obtained in the second case; the current geometrical characteristics are accurately described. In the capillary-free case, we demonstrate that the local total velocity, which is, on average, zero because the flow is counter-current, must be considered in the total flux at the interface to obtain the same level of agreement.

Energy Considerations in the Spreading of LNG on Sea Water

2008 ◽  
Author(s):  
A. Subramani ◽  
S. Jayanti
Keyword(s):  
Heat Transfer ◽  
Sea Water ◽  
Current Model ◽  
Theoretical Models ◽  
Effect Of Temperature ◽  
Test Case ◽  
Hazardous Substance ◽  
Temperature Dependent ◽  
One Dimensional ◽  
Conventional Models

The spreading of an accidental spill of Liquefied Natural Gas (LNG) on sea water has been studied for many years and several theoretical models have been proposed and successfully used. Many modeling techniques have been used by researchers for the spreading of LNG. However, most of these neglect the heat transfer aspects related to the spreading, and the effect of temperature dependent properties such as density, thermal conductivity and specific heat of LNG is not included in the analysis. In the present study, this situation is redressed by including the depth-averaged energy equation in a one-dimensional model of the spreading of LNG on sea water. The thermophysical and transport properties of the fluid are made temperature-dependent and heat transfer to the pool from the water below and the flame above are included. The resulting set of coupled one-dimensional mass, radial momentum and energy balance equations are solved numerically using an explicit, second order-accurate finite difference method-based discretization of the governing equations. Results obtained in the present study show that the incorporation of the variable properties gives significantly improved predictions over conventional models. The predicted results are compared with the experimental results of Raj et al [1], and with a conventional, constant-properties model of Fay [2] for the test case #12. Excellent agreement is found between the current model predictions and the experimental data while the conventional model overpredicts the pool diameter for longer times. It is demonstrated that the present approach is inherently capable of distinguishing between the spreading of different LNG mixtures, and can therefore be readily extended to the analysis of the accidental spill of any other hazardous substance.

scholarly journals Characterization of Bacillus anthracis Germinant Receptors In Vitro

2005 ◽  
Vol 187 (23) ◽  
pp. 8055-8062 ◽  
Author(s):  
Nathan Fisher ◽  
Philip Hanna
Keyword(s):  
Bacillus Anthracis ◽  
Current Model ◽  
Insertion Mutagenesis ◽  
Cell Type ◽  
Dormant Cell ◽  
Temperature Dependent ◽  
Infectious Cycle ◽  
A Current

ABSTRACT Bacillus anthracis begins its infectious cycle as a metabolically dormant cell type, the endospore. Upon entry into a host, endospores rapidly differentiate into vegetative bacilli through the process of germination, thus initiating anthrax. Elucidation of the signals that trigger germination and the receptors that recognize them is critical to understanding the pathogenesis of B. anthracis. Individual mutants deficient in each of the seven putative germinant receptor-encoding loci were constructed via temperature-dependent, plasmid insertion mutagenesis and used to correlate these receptors with known germinant molecules. These analyses showed that the GerK and GerL receptors are jointly required for the alanine germination pathway and also are individually required for recognition of either proline and methionine (GerK) or serine and valine (GerL) as cogerminants in combination with inosine. The germinant specificity of GerS was refined from a previous study in a nonisogenic background since it was required only for germination in response to aromatic amino acid cogerminants. The gerA and gerY loci were found to be dispensable for recognition of all known germinant molecules. In addition, we show that the promoter of each putative germinant receptor operon, except that of the gerA locus, is active during sporulation. A current model of B. anthracis endospore germination is presented.

scholarly journals Capture of the Canary mantle plume material by the Gibraltar arc mantle wedge during slab rollback

2015 ◽  
Vol 201 (3) ◽  
pp. 1717-1721 ◽  
Author(s):  
C.A. Mériaux ◽  
J.C. Duarte ◽  
S.S. Duarte ◽  
W.P. Schellart ◽  
Z. Chen ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Mantle Wedge ◽  
Gravity Current ◽  
Separation Distance ◽  
Western Mediterranean ◽  
Return Flow ◽  
Mantle Flow ◽  
Scaled Model ◽  
Slab Rollback ◽  
Subduction System

Abstract Recent evidence suggests that a portion of the Canary plume travelled northeastwards below the lithosphere of the Atlas Mountains in North Africa towards the Alboran domain and was captured ∼10 Ma ago by the Gibraltar subduction system in the Western Mediterranean. The capture would have been associated with the mantle return flow induced by the westward-retreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the Gibraltar subduction zone. Such material eventually contaminated the subduction related volcanism in the Alboran region. In this work, we use scaled analogue models of slab–plume interaction to investigate the plausibility of the plume capture. An upper-mantle-scaled model combines a narrow (400 km) edge-fixed subduction plate with a laterally offset compositional plume. The subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 × 1350 km2. While the plume head initially spreads axisymmetrically, it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km, before getting dragged towards mantle wedge. When applied to the Canary plume–Gibraltar subduction system, our model supports the observationally based conceptual model that mantle plume material may have been dragged towards the mantle wedge by slab rollback-induced toroidal mantle flow. Using a scaling argument for the spreading of a gravity current within a channel, we also show that more than 1500 km of plume propagation in the sublithospheric Atlas corridor is dynamically plausible.

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