Ice scallops: a laboratory investigation of the ice-water interface
Journal of Fluid Mechanics
Ice scallops are a small-scale (5-20a cm) quasi-periodic ripple pattern that occurs at the ice-water interface. Previous work has suggested that scallops form due to a self-reinforcing interaction between an evolving ice-surface geometry, an adjacent turbulent flow field and the resulting differential melt rates that occur along the interface. In this study, we perform a series of laboratory experiments in a refrigerated flume to quantitatively investigate the mechanisms of scallop formation and evolution in high resolution. Using particle image velocimetry, we probe an evolving ice-water boundary layer at sub-millimetre scales and 15a Hz frequency. Our data reveal three distinct regimes of ice-water interface evolution: a transition from flat to scalloped ice; an equilibrium scallop geometry; and an adjusting scallop interface. We find that scalloped-ice geometry produces a clear modification to the ice-water boundary layer, characterized by a time-mean recirculating eddy feature that forms in the scallop trough. Our primary finding is that scallops form due to a self-reinforcing feedback between the ice-interface geometry and shear production of turbulent kinetic energy in the flow interior. The length of this shear production zone is therefore hypothesized to set the scallop wavelength.
National Science Foundation
morphological instability, solidification/melting, turbulent boundary layers
Moss Landing Marine Laboratories
Mitchell Bushuk, David M. Holland, Timothy P. Stanton, Alon Stern, and Callum Gray. "Ice scallops: a laboratory investigation of the ice-water interface" Journal of Fluid Mechanics (2019): 942-976. https://doi.org/10.1017/jfm.2019.398