Journal articles: 'Gravity currents'

1

Moodie, T. B. "Gravity currents." Journal of Computational and Applied Mathematics 144, no. 1-2 (July 2002): 49–83. http://dx.doi.org/10.1016/s0377-0427(01)00551-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Johnson, Christopher G., and Andrew J. Hogg. "Entraining gravity currents." Journal of Fluid Mechanics 731 (August 19, 2013): 477–508. http://dx.doi.org/10.1017/jfm.2013.329.

Full text

Abstract:

AbstractEntrainment of ambient fluid into a gravity current, while often negligible in laboratory-scale flows, may become increasingly significant in large-scale natural flows. We present a theoretical study of the effect of this entrainment by augmenting a shallow water model for gravity currents under a deep ambient with a simple empirical model for entrainment, based on experimental measurements of the fluid entrainment rate as a function of the bulk Richardson number. By analysing long-time similarity solutions of the model, we find that the decrease in entrainment coefficient at large Richardson number, due to the suppression of turbulent mixing by stable stratification, qualitatively affects the structure and growth rate of the solutions, compared to currents in which the entrainment is taken to be constant or negligible. In particular, mixing is most significant close to the front of the currents, leading to flows that are more dilute, deeper and slower than their non-entraining counterparts. The long-time solution of an inviscid entraining gravity current generated by a lock-release of dense fluid is a similarity solution of the second kind, in which the current grows as a power of time that is dependent on the form of the entrainment law. With an entrainment law that fits the experimental measurements well, the length of currents in this entraining inviscid regime grows with time approximately as ${t}^{0. 447} $. For currents instigated by a constant buoyancy flux, a different solution structure exists in which the current length grows as ${t}^{4/ 5} $. In both cases, entrainment is most significant close to the current front.

APA, Harvard, Vancouver, ISO, and other styles

3

D'Alessio, S. J. D., T. B. Moodie, J. P. Pascal, and G. E. Swaters. "Intrusive Gravity Currents." Studies in Applied Mathematics 98, no. 1 (January 1997): 19–46. http://dx.doi.org/10.1111/1467-9590.00039.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

FLYNN, M. R., and P. F. LINDEN. "Intrusive gravity currents." Journal of Fluid Mechanics 568 (November 10, 2006): 193. http://dx.doi.org/10.1017/s0022112006002734.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Hewitt, Duncan R., and Neil J. Balmforth. "Thixotropic gravity currents." Journal of Fluid Mechanics 727 (June 14, 2013): 56–82. http://dx.doi.org/10.1017/jfm.2013.235.

Full text

Abstract:

AbstractWe present a model for thixotropic gravity currents flowing down an inclined plane that combines lubrication theory for shallow flow with a rheological constitutive law describing the degree of microscopic structure. The model is solved numerically for a finite volume of fluid in both two and three dimensions. The results illustrate the importance of the degree of initial ageing and the spatio-temporal variations of the microstructure during flow. The fluid does not flow unless the plane is inclined beyond a critical angle that depends on the ageing time. Above that critical angle and for relatively long ageing times, the fluid dramatically avalanches downslope, with the current becoming characterized by a structured horseshoe-shaped remnant of fluid at the back and a raised nose at the advancing front. The flow is prone to a weak interfacial instability that occurs along the border between structured and de-structured fluid. Experiments with bentonite clay show broadly similar phenomenological behaviour to that predicted by the model. Differences between the experiments and the model are discussed.

APA, Harvard, Vancouver, ISO, and other styles

6

Bonnecaze, Roger T., Herbert E. Huppert, and John R. Lister. "Particle-driven gravity currents." Journal of Fluid Mechanics 250 (May 1993): 339–69. http://dx.doi.org/10.1017/s002211209300148x.

Full text

Abstract:

Gravity currents created by the release of a fixed volume of a suspension into a lighter ambient fluid are studied theoretically and experimentally. The greater density of the current and the buoyancy force driving its motion arise primarily from dense particles suspended in the interstitial fluid of the current. The dynamics of the current are assumed to be dominated by a balance between inertial and buoyancy forces; viscous forces are assumed negligible. The currents considered are two-dimensional and flow over a rigid horizontal surface. The flow is modelled by either the single- or the two-layer shallow-water equations, the two-layer equations being necessary to include the effects of the overlying fluid, which are important when the depth of the current is comparable to the depth of the overlying fluid. Because the local density of the gravity current depends on the concentration of particles, the buoyancy contribution to the momentum balance depends on the variation of the particle concentration. A transport equation for the particle concentration is derived by assuming that the particles are vertically well-mixed by the turbulence in the current, are advected by the mean flow and settle out through the viscous sublayer at the bottom of the current. The boundary condition at the moving front of the current relates the velocity and the pressure head at that point. The resulting equations are solved numerically, which reveals that two types of shock can occur in the current. In the late stages of all particle-driven gravity currents, an internal bore develops that separates a particle-free jet-like flow in the rear from a dense gravity-current flow near the front. The second type of bore occurs if the initial height of the current is comparable to the depth of the ambient fluid. This bore develops during the early lock-exchange flow between the two fluids and strongly changes the structure of the current and its transport of particles from those of a current in very deep surroundings. To test the theory, several experiments were performed to measure the length of particle-driven gravity currents as a function of time and their deposition patterns for a variety of particle sizes and initial masses of sediment. The comparison between the theoretical predictions, which have no adjustable parameters, and the experimental results are very good.

APA, Harvard, Vancouver, ISO, and other styles

7

HEWITT, I. J., N. J. BALMFORTH, and J. R. DE BRUYN. "Elastic-plated gravity currents." European Journal of Applied Mathematics 26, no. 1 (October 10, 2014): 1–31. http://dx.doi.org/10.1017/s0956792514000291.

Full text

Abstract:

We consider a nonlinear diffusion equation describing the planar spreading of a viscous fluid injected between an elastic sheet and an underlying rigid plane. The dynamics depends sensitively on the physical conditions at the contact line where the sheet is lifted off the plane by the fluid. We explore two possibilities for these conditions (or “regularisations”): a pre-wetted film and a constant-pressure fluid lag (a gas-filled gap between the fluid edge and the contact line). For both flat and inclined planes, we compare numerical and asymptotic solutions, identifying the distinct stages of evolution and the corresponding characteristic rates of spreading.

APA, Harvard, Vancouver, ISO, and other styles

8

Kowal, Katarzyna N., and M. Grae Worster. "Lubricated viscous gravity currents." Journal of Fluid Mechanics 766 (February 10, 2015): 626–55. http://dx.doi.org/10.1017/jfm.2015.30.

Full text

Abstract:

AbstractWe present a theoretical and experimental study of viscous gravity currents lubricated by another viscous fluid from below. We use lubrication theory to model both layers as Newtonian fluids spreading under their own weight in two-dimensional and axisymmetric settings over a smooth rigid horizontal surface and consider the limit in which vertical shear provides the dominant resistance to the flow in both layers. There are contributions from Poiseuille-like flow driven by buoyancy and Couette-like flow driven by viscous coupling between the layers. The flow is self-similar if both fluids are released simultaneously, and exhibits initial transient behaviour when there is a delay between the initiation of flow in the two layers. We solve for both situations and show that the latter converges towards self-similarity at late times. The flow depends on three key dimensionless parameters relating the relative dynamic viscosities, input fluxes and density differences between the two layers. Provided the density difference between the two layers is bounded away from zero, we find an asymptotic solution in which the front of the lubricant is driven by its own gravitational spreading. There is a singular limit of equal densities in which the lubricant no longer spreads under its own weight in the vicinity of its nose and ends abruptly with a non-zero thickness there. We explore various regimes, from thin lubricating layers underneath a more viscous current to thin surface films coating an underlying more viscous current and find that although a thin film does not greatly influence the more viscous current if it forms a surface coating, it begins to cause interesting dynamics if it lubricates the more viscous current from below. We find experimentally that a lubricated gravity current is prone to a fingering instability.

APA, Harvard, Vancouver, ISO, and other styles

9

Nasr-Azadani, M. M., and E. Meiburg. "Gravity currents propagating into shear." Journal of Fluid Mechanics 778 (August 5, 2015): 552–85. http://dx.doi.org/10.1017/jfm.2015.398.

Full text

Abstract:

An analytical vorticity-based model is introduced for steady-state inviscid Boussinesq gravity currents in sheared ambients. The model enforces the conservation of mass and horizontal and vertical momentum, and it does not require any empirical closure assumptions. As a function of the given gravity current height, upstream ambient shear and upstream ambient layer thicknesses, the model predicts the current velocity as well as the downstream ambient layer thicknesses and velocities. In particular, it predicts the existence of gravity currents with a thickness greater than half the channel height, which is confirmed by direct numerical simulation (DNS) results and by an analysis of the energy loss in the flow. For high-Reynolds-number gravity currents exhibiting Kelvin–Helmholtz instabilities along the current/ambient interface, the DNS simulations suggest that for a given shear magnitude, the current height adjusts itself such as to allow for maximum energy dissipation.

APA, Harvard, Vancouver, ISO, and other styles

10

Bonnecaze, Roger T., Mark A. Hallworth, Herbert E. Huppert, and John R. Lister. "Axisymmetric particle-driven gravity currents." Journal of Fluid Mechanics 294 (July 10, 1995): 93–121. http://dx.doi.org/10.1017/s0022112095002825.

Full text

Abstract:

Axisymmetric gravity currents that result when a dense suspension intrudes under a lighter ambient fluid are studied theoretically and experimentally. The dynamics of and deposition from currents flowing over a rigid horizontal surface are determined for the release of either a fixed volume or a constant flux of a suspension. The dynamics of the current are assumed to be dominated by inertial and buoyancy forces, while viscous forces are assumed to be negligible. The fluid motion is modelled by the single-layer axisymmetric shallow-water equations, which neglect the effects of the overlying fluid. An advective transport equation models the distribution of particles in the current, and this distribution determines the local buoyancy force in the shallow-water equations. The transport equation is derived on the assumption that the particles are vertically well-mixed by the turbulence in the current, are advected by the mean flow and settle out through a viscous sublayer at the bottom of the current. No adjustable parameters are needed to specify the theoretical model. The coupled equations of the model are solved numerically, and it is predicted that after an early stage both constant-volume and constant-flux, particle-driven gravity currents develop an internal bore which separates a supercritical particle-free region upstream from a subcritical particle-rich region downstream near the head of the current. For the fixed-volume release, an earlier bore is also predicted to occur very shortly after the initial collapse of the current. This bore transports suspended particles away from the origin, which results in a maximum in the predicted deposition away from the centre.To test the model several laboratory experiments were performed to determine both the radius of an axisymmetric particle-driven gravity current as a function of time and its deposition pattern for a variety of initial particle concentrations, particle sizes, volumes and flow rates. For the release of a fixed volume and of a constant flux of suspension, the comparisons between the experimental results and the theoretical predictions are fairly good. However, for the current of fixed volume, we did not observe the bore predicted to occur shortly after the collapse of the current or the resulting maximum in deposition downstream of the origin. This is unlike the previous study of Bonnecaze et al. (1993) on two-dimensional currents, in which a strong bore was observed during the slumping phase. The radial extent R of the deposit from a fixed-volume current is accurately predicted by the model, and for currents whose particles settle sufficiently slowly, we find that R = 1.9(g′0V3 / v2s)1/8, where V is the volume of the current, vs is the settling velocity of a particle in the suspension and g’0 is the initial reduced gravity of the suspension.

APA, Harvard, Vancouver, ISO, and other styles

11

THOMAS, L. P., B. M. MARINO, and P. F. LINDEN. "Gravity currents over porous substrates." Journal of Fluid Mechanics 366 (July 10, 1998): 239–58. http://dx.doi.org/10.1017/s0022112098001438.

Full text

Abstract:

Results of laboratory experiments are presented in which a fixed volume of homogeneous fluid is suddenly released into another fluid of slightly lower density, over a horizontal thin metallic grid placed a given distance above the solid bottom of a rectangular-cross-section channel. Dense liquid develops as a gravity current over the grid at the same time as it partially flows downwards. The results show that the gravity current loses mass at an exponential rate through the porous substrate with a time constant τ; the front velocity and the head of the current also decrease exponentially. The loss of mass dominates the flow and, in contrast to gravity currents running over solid bottoms, no self-similar inertial regime seems to be developed. A simple model is introduced to explain the scaling law of the loss of mass and the evolution of the front position. The flow evolution depends on the characteristic time of the initial (slumping) phase and the time constant τ, related to the initial conditions and the permeability of the porous substrate, respectively. Qualitative comparisons with other gravity currents with loss of mass, such as particle-driven gravity currents, are provided.

APA, Harvard, Vancouver, ISO, and other styles

12

HESSE, M. A., F. M. ORR, and H. A. TCHELEPI. "Gravity currents with residual trapping." Journal of Fluid Mechanics 611 (September 25, 2008): 35–60. http://dx.doi.org/10.1017/s002211200800219x.

Full text

Abstract:

Motivated by geological carbon dioxide (CO2) storage, we present a vertical-equilibrium sharp-interface model for the migration of immiscible gravity currents with constant residual trapping in a two-dimensional confined aquifer. The residual acts as a loss term that reduces the current volume continuously. In the limit of a horizontal aquifer, the interface shape is self-similar at early and at late times. The spreading of the current and the decay of its volume are governed by power-laws. At early times the exponent of the scaling law is independent of the residual, but at late times it decreases with increasing loss. Owing to the self-similar nature of the current the volume does not become zero, and the current continues to spread. In the hyperbolic limit, the leading edge of the current is given by a rarefaction and the trailing edge by a shock. In the presence of residual trapping, the current volume is reduced to zero in finite time. Expressions for the up-dip migration distance and the final migration time are obtained. Comparison with numerical results shows that the hyperbolic limit is a good approximation for currents with large mobility ratios even far from the hyperbolic limit. In gently sloping aquifers, the current evolution is divided into an initial near-parabolic stage, with power-law decrease of volume, and a later near-hyperbolic stage, characterized by a rapid decay of the plume volume. Our results suggest that the efficient residual trapping in dipping aquifers may allow CO2 storage in aquifers lacking structural closure, if CO2 is injected far enough from the outcrop of the aquifer.

APA, Harvard, Vancouver, ISO, and other styles

13

Hallworth, Mark A., Jeremy C. Phillips, Herbert E. Huppert, and R. Stephen J. Sparks. "Entrainment in turbulent gravity currents." Nature 362, no. 6423 (April 1993): 829–31. http://dx.doi.org/10.1038/362829a0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

JHA, Akhilesh Kumar, Juichiro AKIYAMA, and Masaru URA. "NUMERICAL SIMULATION OF GRAVITY CURRENTS." PROCEEDINGS OF HYDRAULIC ENGINEERING 45 (2001): 979–84. http://dx.doi.org/10.2208/prohe.45.979.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Montesinos, Merced. "Noether currents for BF gravity." Classical and Quantum Gravity 20, no. 16 (July 28, 2003): 3569–75. http://dx.doi.org/10.1088/0264-9381/20/16/303.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Owen, Geraint. "Book Review: Particulate gravity currents." Holocene 13, no. 2 (February 2003): 301–2. http://dx.doi.org/10.1177/095968360301300218.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

TIMMERMANS, MARY-LOUISE E., JOHN R. LISTER, and HERBERT E. HUPPERT. "Compressible particle-driven gravity currents." Journal of Fluid Mechanics 445 (October 16, 2001): 305–25. http://dx.doi.org/10.1017/s0022112001005705.

Full text

Abstract:

Large-scale particle-driven gravity currents occur in the atmosphere, often in the form of pyroclastic flows that result from explosive volcanic eruptions. The behaviour of these gravity currents is analysed here and it is shown that compressibility can be important in flow of such particle-laden gases because the presence of particles greatly reduces the density scale height, so that variations in density due to compressibility are significant over the thickness of the flow. A shallow-water model of the flow is developed, which incorporates the contribution of particles to the density and thermodynamics of the flow. Analytical similarity solutions and numerical solutions of the model equations are derived. The gas–particle mixture decompresses upon gravitational collapse and such flows have faster propagation speeds than incompressible currents of the same dimensions. Once a compressible current has spread sufficiently that its thickness is less than the density scale height it can be treated as incompressible. A simple ‘box-model’ approximation is developed to determine the effects of particle settling. The major effect is that a small amount of particle settling increases the density scale height of the particle-laden mixture and leads to a more rapid decompression of the current.

APA, Harvard, Vancouver, ISO, and other styles

18

HARRIS, THOMAS C., ANDREW J. HOGG, and HERBERT E. HUPPERT. "Polydisperse particle-driven gravity currents." Journal of Fluid Mechanics 472 (November 30, 2002): 333–71. http://dx.doi.org/10.1017/s0022112002002379.

Full text

Abstract:

The intrusion of a polydisperse suspension of particles over a horizontal, rigid boundary is investigated theoretically using both an integral (‘box’) model and the shallow-water equations. The flow is driven by the horizontal pressure gradient associated with the density difference between the intrusion and the surrounding fluid, which is progressively diminished as suspended particles sediment from the flow to the underlying boundary. Each class of particles in a polydisperse suspension has a different settling velocity. The effects of both a discrete and continuous distribution of settling velocities on the propagation of the current are analysed and the results are compared in detail with results obtained by treating the suspension as monodisperse with an average settling velocity. For both models we demonstrate that in many regimes it is insufficient to deduce the behaviour of the suspension from this average, but rather one can characterize the flow using the variance of the settling velocity distribution as well. The shallow-water equations are studied analytically using a novel asymptotic technique, which obviates the need for numerical integration of the governing equations. For a bidisperse suspension we explicitly calculate the flow speed, runout length and the distribution of the deposit, to reveal how the flow naturally leads to a vertical and streamwise segregation of particles even from an initially well-mixed suspension. The asymptotic results are confirmed by comparison with numerical integration of the shallow-water equations and the predictions of this study are discussed in the light of recent experimental results and field observations.

APA, Harvard, Vancouver, ISO, and other styles

19

HUPPERT, HERBERT E. "Gravity currents: a personal perspective." Journal of Fluid Mechanics 554, no. -1 (April 24, 2006): 299. http://dx.doi.org/10.1017/s002211200600930x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Hesse, M. A., F. M. Orr Jr., and H. A. Tchelepi. "Gravity currents with residual trapping." Energy Procedia 1, no. 1 (February 2009): 3275–81. http://dx.doi.org/10.1016/j.egypro.2009.02.113.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Lane-Serff, G. F. "On drag-limited gravity currents." Deep Sea Research Part I: Oceanographic Research Papers 40, no. 8 (August 1993): 1699–702. http://dx.doi.org/10.1016/0967-0637(93)90023-v.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Bonnecaze, R. "Axisymmetric particle-driven gravity currents." International Journal of Multiphase Flow 22 (December 1996): 129. http://dx.doi.org/10.1016/s0301-9322(97)88424-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Bonnecaze, R. "Axisymmetric particle-driven gravity currents." International Journal of Multiphase Flow 22 (December 1996): 130. http://dx.doi.org/10.1016/s0301-9322(97)88436-4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Obukhov, Yuri N., and Guillermo F. Rubilar. "Invariant conserved currents for gravity." Physics Letters B 660, no. 3 (February 2008): 240–46. http://dx.doi.org/10.1016/j.physletb.2007.12.042.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Griffiths, R. W. "Gravity Currents in Rotating Systems." Annual Review of Fluid Mechanics 18, no. 1 (January 1986): 59–89. http://dx.doi.org/10.1146/annurev.fl.18.010186.000423.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Monaghan, J. J. "Gravity currents and solitary waves." Physica D: Nonlinear Phenomena 98, no. 2-4 (November 1996): 523–33. http://dx.doi.org/10.1016/0167-2789(96)00110-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Allen, P. A., R. M. Dorrell, O. G. Harlen, R. E. Thomas, and W. D. McCaffrey. "Pulse propagation in gravity currents." Physics of Fluids 32, no. 1 (January 1, 2020): 016603. http://dx.doi.org/10.1063/1.5130576.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Robinson, T. O., I. Eames, and R. Simons. "Dense gravity currents moving beneath progressive free-surface water waves." Journal of Fluid Mechanics 725 (May 23, 2013): 588–610. http://dx.doi.org/10.1017/jfm.2013.112.

Full text

Abstract:

AbstractThe characteristics of dense gravity currents in coastal regions, where free-surface gravity waves are dominant, have yet to be studied in the laboratory. This paper provides a first insight into the dynamics of dense saline gravity currents moving beneath regular progressive free-surface water waves. The gravity currents were generated by releasing a finite volume of saline into a large wave tank with an established periodic wave field. After the initial collapse, the gravity currents propagated horizontally with two fronts, one propagating in the wave direction and the other against the wave direction. The fronts of the gravity currents oscillated with an amplitude and phase that correlated with the orbital velocities within a region close to the bed. To leading order, the overall length of the gravity current was found to be weakly affected by the wave action and the dynamics of the current could be approximated by simply considering the buoyancy of the released fluid. Other characteristics such as the position of the gravity current centre and the shape of the two leading profiles were found to be significantly affected by the wave action. The centre was displaced at constant speed dependent on the second-order wave-induced mean Lagrangian velocity. For long waves, the centre was advected downstream in the direction of wave propagation owing to the dominance of Stokes drift. For short waves, the gravity current centre moved upstream against the wave direction, as under these wave conditions Stokes drift is negligible at the bed. An asymmetry in the shape of the upstream and downstream current heads was observed, with the gravity current front moving against the waves being much thicker and the front steeper, similar to the case of a current moving in a stream.

APA, Harvard, Vancouver, ISO, and other styles

29

Pegler, Samuel S., Herbert E. Huppert, and Jerome A. Neufeld. "Stratified gravity currents in porous media." Journal of Fluid Mechanics 791 (February 22, 2016): 329–57. http://dx.doi.org/10.1017/jfm.2015.733.

Full text

Abstract:

We consider theoretically and experimentally the propagation in porous media of variable-density gravity currents containing a stably stratified density field, with most previous studies of gravity currents having focused on cases of uniform density. New thin-layer equations are developed to describe stably stratified fluid flows in which the density field is materially advected with the flow. Similarity solutions describing both the fixed-volume release of a distributed density stratification and the continuous input of fluid containing a distribution of densities are obtained. The results indicate that the density distribution of the stratification significantly influences the vertical structure of the gravity current. When more mass is distributed into lighter densities, it is found that the shape of the current changes from the convex shape familiar from studies of the uniform-density case to a concave shape in which lighter fluid accumulates primarily vertically above the origin of the current. For a constant-volume release, the density contours stratify horizontally, a simplification which is used to develop analytical solutions. For currents introduced continuously, the horizontal velocity varies with vertical position, a feature which does not apply to uniform-density gravity currents in porous media. Despite significant effects on vertical structure, the density distribution has almost no effect on overall horizontal propagation, for a given total mass. Good agreement with data from a laboratory study confirms the predictions of the model.

APA, Harvard, Vancouver, ISO, and other styles

30

Hogg, Charlie A. R., Stuart B. Dalziel, Herbert E. Huppert, and Jörg Imberger. "Inclined gravity currents filling basins: The influence of Reynolds number on entrainment into gravity currents." Physics of Fluids 27, no. 9 (September 2015): 096602. http://dx.doi.org/10.1063/1.4930544.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Konopliv, Nathan, and Eckart Meiburg. "Double-diffusive lock-exchange gravity currents." Journal of Fluid Mechanics 797 (May 24, 2016): 729–64. http://dx.doi.org/10.1017/jfm.2016.300.

Full text

Abstract:

Double-diffusive lock-exchange gravity currents in the fingering regime are explored via two- and three-dimensional Navier–Stokes simulations in the Boussinesq limit. Even at modest Reynolds numbers, for which single-diffusive gravity currents remain laminar, double-diffusive currents are seen to give rise to pronounced small-scale fingering convection. The front velocity of these currents exhibits a non-monotonic dependence on the diffusivity ratio and the initial stability ratio. Strongly double-diffusive currents lose both heat and salinity more quickly than weakly double-diffusive ones, and they lose salinity more quickly than heat, so that the density difference driving them increases. This differential loss of heat and salinity furthermore results in the emergence of strong local density maxima and minima along the top and bottom walls in the gate region, which in turn promote the formation of secondary, counterflowing currents along the walls. These secondary currents cause the flow to develop a three-layer structure. The late stages of the flow are dominated by currents flowing oppositely to the original ones. Three-dimensional simulation results are consistent with the trends observed in a two-dimensional parametric study. A detailed analysis of the energy budget demonstrates that strongly double-diffusive currents can release several times their initially available potential energy, and convert large amounts of internal energy into mechanical energy via scalar diffusion. Scaling arguments based on the simulation results suggest that even low Reynolds number double-diffusive gravity currents are governed by a balance of buoyancy and turbulent drag.

APA, Harvard, Vancouver, ISO, and other styles

32

WHITE, BRIAN L., and KARL R. HELFRICH. "Gravity currents and internal waves in a stratified fluid." Journal of Fluid Mechanics 616 (December 10, 2008): 327–56. http://dx.doi.org/10.1017/s0022112008003984.

Full text

Abstract:

A steady theory is presented for gravity currents propagating with constant speed into a stratified fluid with a general density profile. Solution curves for front speed versus height have an energy-conserving upper bound (the conjugate state) and a lower bound marked by the onset of upstream influence. The conjugate state is the largest-amplitude nonlinear internal wave supported by the ambient stratification, and in the limit of weak stratification approaches Benjamin's energy-conserving gravity current solution. When the front speed becomes critical with respect to linear long waves generated above the current, steady solutions cannot be calculated, implying upstream influence. For non-uniform stratification, the critical long-wave speed exceeds the ambient long-wave speed, and the critical-Froude-number condition appropriate for uniform stratification must be generalized. The theoretical results demonstrate a clear connection between internal waves and gravity currents. The steady theory is also compared with non-hydrostatic numerical solutions of the full lock release initial-value problem. Some solutions resemble classic gravity currents with no upstream disturbance, but others show long internal waves propagating ahead of the gravity current. Wave generation generally occurs when the stratification and current speed are such that the steady gravity current theory fails. Thus the steady theory is consistent with the occurrence of either wave-generating or steady gravity solutions to the dam-break problem. When the available potential energy of the dam is large enough, the numerical simulations approach the energy-conserving conjugate state. Existing laboratory experiments for intrusions and gravity currents produced by full-depth lock exchange flows over a range of stratification profiles show excellent agreement with the conjugate state solutions.

APA, Harvard, Vancouver, ISO, and other styles

33

Lee, Jae-Ryong, S. Balachandar, and Man-Yeong Ha. "Direct Numerical Simulation of Gravity Currents." Transactions of the Korean Society of Mechanical Engineers B 30, no. 5 (May 1, 2006): 422–29. http://dx.doi.org/10.3795/ksme-b.2006.30.5.422.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Birman, V. K., and E. Meiburg. "High-resolution simulations of gravity currents." Journal of the Brazilian Society of Mechanical Sciences and Engineering 28, no. 2 (June 2006): 169–73. http://dx.doi.org/10.1590/s1678-58782006000200006.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Marleau, Larissa J., Morris R. Flynn, and Bruce R. Sutherland. "Gravity currents propagating up a slope." Physics of Fluids 26, no. 4 (April 2014): 046605. http://dx.doi.org/10.1063/1.4872222.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Dai, Albert. "Gravity Currents Propagating on Sloping Boundaries." Journal of Hydraulic Engineering 139, no. 6 (June 2013): 593–601. http://dx.doi.org/10.1061/(asce)hy.1943-7900.0000716.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Waltham, D. "Flow Transformations in Particulate Gravity Currents." Journal of Sedimentary Research 74, no. 1 (January 1, 2004): 129–34. http://dx.doi.org/10.1306/062303740129.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Sutherland, Bruce R., Delyle Polet, and Margaret Campbell. "Gravity currents shoaling on a slope." Physics of Fluids 25, no. 8 (August 2013): 086604. http://dx.doi.org/10.1063/1.4818440.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Mehta, A. P., B. R. Sutherland, and P. J. Kyba. "Interfacial gravity currents. II. Wave excitation." Physics of Fluids 14, no. 10 (October 2002): 3558–69. http://dx.doi.org/10.1063/1.1503355.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Sahin, D., N. Antar, and T. Ozer. "Lie group analysis of gravity currents." Nonlinear Analysis: Real World Applications 11, no. 2 (April 2010): 978–94. http://dx.doi.org/10.1016/j.nonrwa.2009.01.039.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

SHIN, J. O., S. B. DALZIEL, and P. F. LINDEN. "Gravity currents produced by lock exchange." Journal of Fluid Mechanics 521 (December 25, 2004): 1–34. http://dx.doi.org/10.1017/s002211200400165x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

MARINO, B. M., L. P. THOMAS, and P. F. LINDEN. "The front condition for gravity currents." Journal of Fluid Mechanics 536 (July 26, 2005): 49–78. http://dx.doi.org/10.1017/s0022112005004933.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Montgomery, P. J., and T. B. Moodie. "Two‐layer Gravity Currents with Topography." Studies in Applied Mathematics 102, no. 3 (April 1999): 221–66. http://dx.doi.org/10.1111/1467-9590.00110.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

ROSS, ANDREW N., STUART B. DALZIEL, and P. F. LINDEN. "Axisymmetric gravity currents on a cone." Journal of Fluid Mechanics 565 (September 28, 2006): 227. http://dx.doi.org/10.1017/s0022112006001601.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Hogg, Andrew J., Mohamad M. Nasr-Azadani, Marius Ungarish, and Eckart Meiburg. "Sustained gravity currents in a channel." Journal of Fluid Mechanics 798 (June 10, 2016): 853–88. http://dx.doi.org/10.1017/jfm.2016.343.

Full text

Abstract:

Gravitationally driven motion arising from a sustained constant source of dense fluid in a horizontal channel is investigated theoretically using shallow-layer models and direct numerical simulations of the Navier–Stokes equations, coupled to an advection–diffusion model of the density field. The influxed dense fluid forms a flowing layer underneath the less dense fluid, which initially filled the channel, and in this study its speed of propagation is calculated; the outflux is at the end of the channel. The motion, under the assumption of hydrostatic balance, is modelled using a two-layer shallow-water model to account for the flow of both the dense and the overlying less dense fluids. When the relative density difference between the fluids is small (the Boussinesq regime), the governing shallow-layer equations are solved using analytical techniques. It is demonstrated that a variety of flow-field patterns are feasible, including those with constant height along the length of the current and those where the height varies continuously and discontinuously. The type of solution realised in any scenario is determined by the magnitude of the dimensionless flux issuing from the source and the source Froude number. Two important phenomena may occur: the flow may be choked, whereby the excess velocity due to the density difference is bounded and the height of the current may not exceed a determined maximum value, and it is also possible for the dense fluid to completely displace all of the less dense fluid originally in the channel in an expanding region close to the source. The onset and subsequent evolution of these types of motions are also calculated using analytical techniques. The same range of phenomena occurs for non-Boussinesq flows; in this scenario, the solutions of the model are calculated numerically. The results of direct numerical simulations of the Navier–Stokes equations are also reported for unsteady two-dimensional flows in which there is an inflow of dense fluid at one end of the channel and an outflow at the other end. These simulations reveal the detailed mechanics of the motion and the bulk properties are compared with the predictions of the shallow-layer model to demonstrate good agreement between the two modelling strategies.

APA, Harvard, Vancouver, ISO, and other styles

46

Hacker, J., P. F. Linden, and S. B. Dalziel. "Mixing in lock-release gravity currents." Dynamics of Atmospheres and Oceans 24, no. 1-4 (January 1996): 183–95. http://dx.doi.org/10.1016/0377-0265(95)00443-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Birman, V. K., E. Meiburg, and M. Ungarish. "On gravity currents in stratified ambients." Physics of Fluids 19, no. 8 (August 2007): 086602. http://dx.doi.org/10.1063/1.2756553.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Ottolenghi, L., P. Prestininzi, A. Montessori, C. Adduce, and M. La Rocca. "Lattice Boltzmann simulations of gravity currents." European Journal of Mechanics - B/Fluids 67 (January 2018): 125–36. http://dx.doi.org/10.1016/j.euromechflu.2017.09.003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Gratton, Julio, and Claudio Vigo. "Self-similar gravity currents with variable inflow revisited: plane currents." Journal of Fluid Mechanics 258 (January 10, 1994): 77–104. http://dx.doi.org/10.1017/s0022112094003241.

Full text

Abstract:

We use shallow-water theory to study the self-similar gravity currents that describe the intrusion of a heavy fluid below a lighter ambient fluid. We consider in detail the case of currents with planar symmetry produced by a source with variable inflow, such that the volume of the intruding fluid varies in time according to a power law of the type tα. The resistance of the ambient fluid is taken into account by a boundary condition of the von Kármán type, that depends on a parameter β that is a function of the density ratio of the fluids. The flow is characterized by β, α, and the Froude number [Fscr ]0 near the source. We find four kinds of self-similar solutions: subcritical continuous solutions (Type I), continuous solutions with a supercritical-subcritical transition (Type II), discontinuous solutions (Type III) that have a hydraulic jump, and discontinuous solutions having hydraulic jumps and a subcritical-supercritical transition (Type IV). The current is always subcritical near the front, but near the source it is subcritical ([Fscr ]0 < 1) for Type I currents, and supercritical ([Fscr ]0 > 1) for Types II, III, and IV. Type I solutions have already been found by other authors, but Type II, III, and IV currents are novel. We find the intervals of parameters for which these solutions exist, and discuss their properties. For constant-volume currents one obtains Type I solutions for any β that, when β > 2, have a ‘dry’ region near the origin. For steady inflow one finds Type I currents for O < β < ∞ and Type II and III Currents for and β, if [Fscr ]0 is sufficiently large.

APA, Harvard, Vancouver, ISO, and other styles

50

BONNECAZE, ROGER T., and JOHN R. LISTER. "Particle-driven gravity currents down planar slopes." Journal of Fluid Mechanics 390 (July 10, 1999): 75–91. http://dx.doi.org/10.1017/s0022112099004917.

Full text

Abstract:

Particle-driven gravity currents, as exemplified by either turbidity currents in the ocean or ignimbrite flows in the atmosphere, are buoyancy-driven flows due to a suspension of dense particles in an ambient fluid. We present a theoretical study on the dynamics of and deposition from a turbulent current flowing down a uniform planar slope from a constant-flux point source of particle-laden fluid. The flow is modelled using the shallow-water equations, including the effects of bottom friction and entrainment of ambient fluid, coupled to an equation for the transport and settling of the particles. Two flow regimes are identified. Near the source and for mild slopes, the flow is dominated by a balance between buoyancy and bottom friction. Further downstream and for steeper slopes, entrainment also affects the behaviour of the current. Similarity solutions are also developed for the simple cases of homogeneous gravity currents with no settling of particles in the friction-dominated and entrainment-dominated regimes. Estimates of the width and length of the deposit from a monodisperse particle-driven gravity current with settling are derived from scaling analysis for each regime, and the contours of the depositional patterns are determined from numerical solution of the governing equations.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Gravity currents'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles