Gravity currents and intrusions

A dense gravity current propagating in a two-layer stratified ambient. The left-hand side images show experimental snapshots; the right-hand side images are the corresponding numerical simulation output. (From the 2010 Master's thesis of A.W. Tan).


A gravity current is produced when a mass of fluid flows horizontally into a second fluid of greater or lesser density. Such density differences may result from disparities of solute, sediment or heat content as often arise in natural or industrial settings. Common examples of gravity currents include sea-breeze fronts, saline wedges within estuaries and (in the non-Boussinesq case) pyroclastic or tailings slurry flow down a gentle incline.

Whereas the problem of gravity current flow along a rigid boundary has been well-studied, less is known about intrusive gravity currents or intrusions, which propagate along a density interface in either a two-layer, multi-layer or continuously stratified ambient. In particular, for "non-equilibrium" intrusions, the intrusion density is larger or smaller than the mean environmental density resulting in interfacial waves ahead and behind the intrusion front. Working with Bruce R. Sutherland (Univ. of Alberta), Paul F. Linden (Univ. of Cambridge) and others, I have examined the waves' impact on the duration and properties of the initial slumping phase of motion during which the intrusion travels at roughly constant speed. As summarized in detail in the publications listed below, these wave-current interactions give rise to interesting behavior that often times complicates modeling efforts.

Note that numerical modeling is done using the open source code Diablo, which was developed by John R. Taylor and Thomas Bewley.

Movies:
  • Laboratory movie showing the propagation of a gravity over topography and through a two-layer stratified ambient -- from Nicholson & Flynn 2015
  • Laboratory movie showing an axisymmetric gravity current in a two-layer stratified medium (supercritical flow) -- from Sahuri et al. 2015
  • Laboratory movie showing an axisymmetric gravity current in a two-layer stratified medium (subcritical flow) -- from Sahuri et al. 2015
  • Numerical simulation of a rectilinear non-equilibrium intrusion traveling along a sharp density interface
  • Numerical simulation of a rectilinear gravity current in a two-layer stratified medium (supercritical flow)
  • Numerical simulation of a rectilinear gravity current in a two-layer stratified medium (subcritical flow)

    (Not so) recent presentations:
  • Gravity current flow in density-stratified media and porous media filling box flow: towards improved models of environmental transport (.pdf)
  • Gravity currents in two-layer stratified media (.pdf)

    Recent (and not-so-recent) publications:
  • Tailwater gravity currents and their connection to perfectly subcritical flow: laboratory experiments and shallow-water and direct numerical solutions (Env. Fluid Mech., 20, with M.S. Baker and M. Ungarish) (link)

  • Gravity current flow over sinusoidal topography in a two-layer ambient (Phys. Fluids, 27, with M. Nicholson) (.pdf)
    [Copyright 2015 American Inst. of Physics. The above article may be downloaded for personal use only. Any other use requires prior permission of the author and the AIP. The above article may be found at http://link.aip.org/link/?PHF/27/096603]

  • Axisymmetric gravity currents in two-layer density-stratified media (Environ. Fluid Mech., 15, with R.M. Sahuri, A.K. Kaminski and M. Ungarish) (link)

  • Gravity currents propagating up a slope in a two-layer fluid (Phys. Fluids, 27, with L.J. Marleau and B.R. Sutherland) (.pdf)
    [Copyright 2015 American Inst. of Physics. The above article may be downloaded for personal use only. Any other use requires prior permission of the author and the AIP. The above article may be found at http://link.aip.org/link/?PHF/27/036601]

  • Gravity currents propagating up a slope (Phys. Fluids, 26, with L.J. Marleau and B.R. Sutherland) (.pdf)
    [Copyright 2014 American Inst. of Physics. The above article may be downloaded for personal use only. Any other use requires prior permission of the author and the AIP. The above article may be found at http://link.aip.org/link/?PHF/26/046605]

  • Gravity currents in a two-layer stratified ambient: The theory for the steady-state (front condition) and lock-released flows, and experimental confirmations (Phys. Fluids, 24, with M. Ungarish and A.W. Tan) (.pdf)
    [Copyright 2012 American Inst. of Physics. The above article may be downloaded for personal use only. Any other use requires prior permission of the author and the AIP. The above article may be found at http://link.aip.org/link/?PHF/24/026601]

  • Gravity currents in two-layer stratified media (Environ. Fluid Mech., 11, with A.W. Tan, D.S. Nobes and B.A. Fleck) (link)

  • The dynamics of steady, partial-depth intrusive gravity currents (Atmosphere-Ocean 46, with T. Boubarne and P. F. Linden) (link)

  • Intrusive gravity currents (J. Fluid Mech. 568, with P. F. Linden) (link)

  • Internal wave excitation from a collapsing mixed region (Deep-Sea Res. II 51, with B. R. Sutherland and K. Dohan) (link)

  • Intrusive gravity currents and internal gravity wave generation in stratified fluid (J. Fluid Mech. 514, with B. R. Sutherland) (link)

  • Intrusive gravity currents in two-layer fluids (J. Fluid Mech. 514, with B. R. Sutherland and P. J. Kyba) (link)