Journal ArticleDOI
Gravity currents in two-layer stratified media
TLDR
In this paper, an analytical, experimental and numerical study of boundary gravity currents propagating through a two-layer stratified ambient of finite vertical extent is presented, where gravity currents are assumed to originate from a lock-release apparatus; the (heavy) gravity current fluid is assumed to span the entire channel depth, H, at the initial instant.Abstract:
An analytical, experimental and numerical study of boundary gravity currents propagating through a two-layer stratified ambient of finite vertical extent is presented. Gravity currents are supposed to originate from a lock-release apparatus; the (heavy) gravity current fluid is assumed to span the entire channel depth, H, at the initial instant. Our theoretical discussion considers slumping, supercritical gravity currents, i.e. those that generate an interfacial disturbance whose speed of propagation matches the front speed, and follows from the classical analysis of Benjamin (J Fluid Mech 31:209–248, 1968). In contrast to previous investigations, we argue that the interfacial disturbance must be parameterized so that its amplitude can be straightforwardly determined from the ambient layer depths. Our parameterization is based on sensible physical arguments; its accuracy is confirmed by comparison against experimental and numerical data. More generally, measured front speeds show positive agreement with analogue model predictions, which remain strictly single-valued. From experimental and numerical observations of supercritical gravity currents, it is noted that this front speed is essentially independent of the interfacial thickness, δ, even in the limiting case where δ = H so that the environment is comprised of a uniformly stratified ambient with no readily discernible upper or lower ambient layer. Conversely, when the gravity current is subcritical, there is a mild increase of front speed with δ. Our experiments also consider the horizontal distance, X, at which the front begins to decelerate. The variation of X with the interface thickness and the depths and densities of the ambient layers is discussed. For subcritical gravity currents, X may be as small as three lock lengths whereas with supercritical gravity currents, the gravity current may travel long distances at constant speed, particularly as the lower layer depth diminishes.read more
Citations
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Journal ArticleDOI
A general description of a gravity current front propagating in a two-layer stratified fluid
Brian White,Karl R. Helfrich +1 more
TL;DR: In this article, the authors describe the behavior of a gravity current propagating into a two-layer stratified ambient fluid, with particular emphasis on the front condition linking the thickness of the gravity current to its speed of propagation and the transfer of energy to upstream disturbances.
Journal ArticleDOI
LES of lock-exchange compositional gravity currents: a brief review of some recent results
TL;DR: In this paper, a 3D Large Eddy Simulation (LES) of bottom-propagating compositional Boussinesq currents in lock-exchange configurations was used to provide a detailed description of the structure of the current, to discuss the role of the large-scale coherent structures, and to predict the evolution of the front velocity over the different stages of current propagation.
Journal ArticleDOI
Generation of internal solitary waves by frontally forced intrusions in geophysical flows
TL;DR: A rarely observed natural case of the birth of internal solitary waves from a frontally forced interfacial gravity current intruding into a two-layer and vertically sheared background environment is reported in the Saguenay Fjord, Canada.
Journal Article
Generation of internal solitary waves by frontally forced intrusions in geophysical flows
TL;DR: In this paper, the authors reported a rarely observed natural case of the birth of internal solitary waves from a frontally forced interfacial gravity current intruding into a two-layer and vertically sheared background environment.
Journal ArticleDOI
Gravity currents in a two-layer stratified ambient: The theory for the steady-state (front condition) and lock-released flows, and experimental confirmations
TL;DR: In this paper, the authors considered the propagation of a gravity current of density ρc at the bottom of a two-layer stratified ambient in a horizontal channel of height H, in the high-Reynolds number Boussinesq domain.
References
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Gravity currents produced by instantaneous releases of a heavy fluid in a rectangular channel
James W. Rottman,J. E. Simpson +1 more
TL;DR: In this paper, a finite volume of homogeneous fluid was released instantaneously into another fluid of slightly lower density and the experiments were performed in a channel of rectangular cross-section, and the two fluids used were salt water and fresh water.