Gravity Currents Produced by Sudden Release of a Fixed Volume of Heavy Fluid

1996 ◽  
Vol 96 (4) ◽  
pp. 359-385 ◽  
Author(s):  
S. J. D. D'Alessio ◽  
T. Bryant Moodie ◽  
J. P. Pascal ◽  
G. E. Swaters
Keyword(s):  
Gravity Currents ◽  
Heavy Fluid ◽  
Fixed Volume ◽  
Sudden Release

High-resolution simulations of cylindrical gravity currents in a rotating system

2016 ◽  
Vol 806 ◽  
pp. 71-101 ◽  
Author(s):  
Albert Dai ◽  
Ching-Sen Wu
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Three Dimensional ◽  
Gravity Currents ◽  
The Body ◽  
Heavy Fluid ◽  
Rotating System ◽  
Maximum Radius ◽  
Inertia Forces

Cylindrical gravity currents, produced by a full-depth lock release, in a rotating system are investigated by means of three-dimensional high-resolution simulations of the incompressible variable-density Navier–Stokes equations with the Coriolis term and using the Boussinesq approximation for a small density difference. Here, the depth of the fluid is chosen to be the same as the radius of the cylindrical lock and the ambient fluid is non-stratified. Our attention is focused on the situation when the ratio of Coriolis to inertia forces is not large, namely $0.1\leqslant {\mathcal{C}}\leqslant 0.3$, and the non-rotating case, namely ${\mathcal{C}}=0$, is also briefly considered. The simulations reproduce the major features observed in the laboratory and provide more detailed flow information. After the heavy fluid contained in a cylindrical lock is released in a rotating system, the influence of the Coriolis effects is not significant during the initial one-tenth of a revolution of the system. During the initial one-tenth of a revolution of the system, Kelvin–Helmholtz vortices form and the rotating cylindrical gravity currents maintain nearly perfect axisymmetry. Afterwards, three-dimensionality of the flow quickly develops and the outer rim of the spreading heavy fluid breaks away from the body of the current, which gives rise to the maximum dissipation rate in the system during the entire adjustment process. The detached outer rim of heavy fluid then continues to propagate outward until a maximum radius of propagation is attained. The body of the current exhibits a complex contraction–relaxation motion and new outwardly propagating pulses form regularly in a period slightly less than half-revolution of the system. Depending on the ratio of Coriolis to inertia forces, such a contraction–relaxation motion may be initiated after or before the attainment of a maximum radius of propagation. In the contraction–relaxation motion of the heavy fluid, energy is transformed between potential energy and kinetic energy, while it is mainly the kinetic energy that is consumed by the dissipation. As a new pulse initially propagates outward, the potential energy in the system increases at the expense of decreasing kinetic energy, until a local maximum of potential energy is reached. During the latter part of the new pulse propagation, the kinetic energy in the system increases at the expense of decreasing potential energy, until a local minimum of potential energy is reached and another new pulse takes form. With the use of three-dimensional high-resolution simulations, the lobe-and-cleft structure at the advancing front can be clearly observed. The number of lobes is maintained only for a limited period of time before merger between existing lobes occurs when a maximum radius of propagation is approached. The high-resolution simulations complement the existing shallow-water formulation, which accurately predicts many important features and provides insights for rotating cylindrical gravity currents with good physical assumptions and simple mathematical models.

scholarly journals On gravity currents of fixed volume that encounter a down-slope or up-slope bottom

2019 ◽  
Vol 31 (9) ◽  
pp. 096604 ◽  
Author(s):  
T. Zemach ◽  
M. Ungarish ◽  
A. Martin ◽  
M. E. Negretti
Keyword(s):  
Gravity Currents ◽  
Slope Bottom ◽  
Fixed Volume

Experiments on gravity currents propagating down slopes. Part 1. The release of a fixed volume of heavy fluid from an enclosed lock into an open channel

2007 ◽  
Vol 584 ◽  
pp. 433-453 ◽  
Author(s):  
T. MAXWORTHY ◽  
R. I. NOKES
Keyword(s):  
Open Channel ◽  
Gravity Current ◽  
Gravity Currents ◽  
Velocity Versus ◽  
Heavy Fluid ◽  
Velocity Measurements ◽  
Video Images ◽  
Maximum Angle ◽  
Time Histories ◽  
Vertical Slice

Gravity currents formed by the release of heavy fluid from an enclosed lock on a sloping open channel were investigated experimentally. The experiments were conducted in a channel that had a running length of 13 lock depths, and could be inclined to a maximum angle of 17°. The release of heavy dyed salt solution from a lock with an aspect ratio (height to length) of 0.5, was examined using video images to determine the front velocity, and a particle-tracking technique was used to measure the two-dimensional velocity field in a vertical slice through the centre of the evolving current. The gravity current head velocity increased with time and downstream distance to a maximum at approximately 10 lock depths from the front of the lock. Flow visualization and the velocity measurements have shown that during the acceleration phase the head was being fed by a following current that increased its buoyancy as it propagated downstream. A modified version of the theory of P. Beghin, E. J. Hopfinger and R. E. Britter (J. Fluid Mech.vol. 107, 1981, p. 407) in which the measured increase in buoyancy was used, instead of the original assumption of constant buoyancy, gave results that agreed closely with the experimental velocity versus time histories.

scholarly journals Axisymmetric particle-driven gravity currents

1995 ◽  
Vol 294 ◽  
pp. 93-121 ◽  
Author(s):  
Roger T. Bonnecaze ◽  
Mark A. Hallworth ◽  
Herbert E. Huppert ◽  
John R. Lister
Keyword(s):  
Transport Equation ◽  
Shallow Water ◽  
Shallow Water Equations ◽  
Gravity Current ◽  
Gravity Currents ◽  
Mean Flow ◽  
Constant Flux ◽  
Coupled Equations ◽  
Fixed Volume ◽  
Free Region

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.

Secondary generation of breaking internal waves in confined basins by gravity currents

2021 ◽  
Vol 917 ◽  
Author(s):  
Yukinobu Tanimoto ◽  
Nicholas T. Ouellette ◽  
Jeffrey R. Koseff
Keyword(s):  
Internal Waves ◽  
Gravity Currents

Abstract

Gravity currents produced by lock exchange

2004 ◽  
Vol 521 ◽  
pp. 1-34 ◽  
Author(s):  
J. O. SHIN ◽  
S. B. DALZIEL ◽  
P. F. LINDEN
Keyword(s):  
Gravity Currents
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