Removal of a dense bottom layer by a gravity current

Zhu, Rui; He, Zhiguo; Meiburg, Eckart

doi:10.1017/jfm.2021.234

Cited by 4 publications

(1 citation statement)

References 31 publications

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“…This suggests that a single-layer gravity current with a small aspect ratio will transfer approximately of its initial energy to the ambient fluid, as the lock fluid collapses and forms the gravity current. A similar conclusion can also be found from Zhu, He & Meiburg (2021). On the other hand, the energy variation of the upper layer mainly comes from the decrease of the potential energy , which is shown in figure 13.…”

Section: Resultssupporting

confidence: 88%

Mixing, entrainment and energetics of gravity currents released from two-layer stratified locks

Zhu

He²,

Meiburg³

2023

J. Fluid Mech.

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We conduct three-dimensional direct numerical simulations to investigate the mixing, entrainment and energy budgets of gravity currents emerging from two-layer stratified locks. Depending on the density and layer thickness ratios, we find that either the upper layer or lower layer fluid can propagate faster, and that the density structure of the overall gravity current can range from strongly stratified to near-complete mixing. We furthermore observe that intermediate values of the density ratio can maximise mixing between the gravity current layers. Based on the vorticity budget, we propose a theoretical model for predicting the overall gravity current height, along with the front velocity of the two layers, for situations in which the lower layer moves faster than the upper layer. The model identifies the role of the height and thickness ratios in determining the velocity structure of the current, and it clarifies the dynamics of the ambient counter-current. A detailed analysis of the energy budget quantifies the conversion of potential into kinetic energy as a function of the governing parameters, along with the energy transfer between the different layers of the gravity current and the ambient fluid. Depending on the values of the density and layer thickness ratios, we find that the lower lock layer can gain or lose energy, whereas the upper layer always loses energy.

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Section: Resultssupporting

confidence: 88%

Mixing, entrainment and energetics of gravity currents released from two-layer stratified locks

Zhu

He²,

Meiburg³

2023

J. Fluid Mech.

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Impacts of Rigid Vegetation on Gravity Currents Propagating in a Stratified Environment

Lin,

Han,

et al. 2023

J. Hydraul. Eng.

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Coherent structures, turbulence intermittency, and anisotropy of gravity currents propagating on a rough and porous bed

et al. 2023

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This study experimentally investigated the impacts of rough and porous (RP) bed and sedimentation processes on the coherent structures, turbulence intermittency, and anisotropy of saline and turbidity currents. Results reveal that the local current concentration responds immediately (saline current) or languidly (turbidity current) to turbulence bursting events. Inside the dense current, the turbulent momentum fluxes in streamwise and vertical directions transfer downstream and downward, which favor the sweep events. Inside the ambient water, the turbulent momentum fluxes in streamwise and vertical directions transfer upstream and upward, contributing to the formation of ejection events. At the current-ambient water interface, the turbulent momentum fluxes in streamwise and vertical directions do not tend to transfer in particular directions resulting in almost equal quantities of sweep and ejection events. The Gram-Charlier series expansion is strictly applicable to probability density functions (PDFs) of the sweep and ejection events but not suitable ideally for PDFs of the outward and inward interaction events. The primary anisotropy invariant map (AIM) of gravity currents starts from the two-component plain strain limit (near the bed). It is followed by the three-dimensional isotropy (inside the dense current and ambient water) and the axisymmetric contraction limit (current-ambient water interface). Finally, it ends in two-dimensional isotropy (near the free surface). This AIM is sensitive to the RP boundary and the sedimentation processes. Along the streamwise direction, the RP boundary causes alternations between the anisotropic and isotropic turbulence, but the arranged pattern of the rough units determines the period of this alternation.

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Removal of a dense bottom layer by a gravity current

Abstract: Abstract

Cited by 4 publications

References 31 publications

Mixing, entrainment and energetics of gravity currents released from two-layer stratified locks

Mixing, entrainment and energetics of gravity currents released from two-layer stratified locks

Impacts of Rigid Vegetation on Gravity Currents Propagating in a Stratified Environment

Coherent structures, turbulence intermittency, and anisotropy of gravity currents propagating on a rough and porous bed

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