EGU2020-19054
https://doi.org/10.5194/egusphere-egu2020-19054
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Ice melting in a turbulent stratified shear flow

Louis-Alexandre Couston1, Eric Hester2, Benjamin Favier3, Adrian Jenkins1, and Paul Holland1
Louis-Alexandre Couston et al.
  • 1British Antarctic Survey, Cambridge, UK (loton@bas.ac.uk)
  • 2Department of Mathematics and Statistics, University of Sydney, Australia
  • 3Institut de Recherche sur les Phénomènes Hors Equilibre, Aix-Marseille Université, Marseille, France

In this talk I will present preliminary results of direct numerical simulations of ice melting in a turbulent stratified shear flow. The model solves the evolution of the turbulent fluid phase and of the diffusive solid ice phase, due to melting and freezing, in a fully coupled way. This is done by combining a Direct Numerical Simulation (DNS) code with a novel formulation of the equations for the solid and liquid phases of water based on the phase-field method. DNS enables turbulent motions to be simulated without approximation, i.e. solving Navier Stokes equations, while the phase-field method allows the ice-ocean interface to be rough and evolve in response to melting. I will present results on the turbulent boundary layer and on the self-generated basal topography at the ice-water interface. The ultimate goal of this work is to propose a new DNS-based parameterization of the melting process at rough ice-ocean boundaries that takes into account the effects of temperature and salt stratification, and flow velocities.

How to cite: Couston, L.-A., Hester, E., Favier, B., Jenkins, A., and Holland, P.: Ice melting in a turbulent stratified shear flow, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19054, https://doi.org/10.5194/egusphere-egu2020-19054, 2020

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Display material version 1 – uploaded on 22 Apr 2020
  • CC1: Comment on EGU2020-19054, Leo Middleton, 29 Apr 2020

    Hi Louis, thanks so much for your presentation. I had some questions regarding how this relates to previous studies of ice ripples. The Bushuk et al. 2019 paper cites a body of work investigating transerse ripples that can form spontaneously at high flow speeds or can be forced at low flow speeds. It seems the arguement is that this ripple instability can lead to scallops, so it's interesting that your study finds an alternative structure (streamwise ripples) that are the natural structure for low flow speeds. Would it be possible to initiate your simulations with a perturbation to achieve ripples (like in Gilpin 1979)? If so, maybe the transverse and streamwise ripple mechanisms couple in some way to give you scallops? Probably too simple an explanation but interested to know if you've tried something similar.

    • AC1: Reply to CC1, Louis-Alexandre Couston, 29 Apr 2020

      Hi Leo. Thank you for your comment. Short answer is yes we can try to force the transverse ripple instability by starting the simulations with a transverse bump or trough as in Gilpin's experiments and no we haven't tried it (yet). However, there is no guarantee that transverse ripples would survive as the dominant topographical features over long time scales even with such an initial transverse bump or trough. The ultimate end state probably varies with water temperature (which is kind of large in our experiments) and flow velocity. Note that streamwise streaks and vortices are likely common features of wall-bounded flows at both low and large speeds (please let me know if I am mistaken). Thanks again!