Ice scallops: a laboratory investigation of the ice–water interface. (25th August 2019)

• Record Type: Journal Article
• Authors: Bushuk, Mitchell; Holland, David M.; Stanton, Timothy P.; Stern, Alon; Gray, Callum
• Is Part Of: Journal of fluid mechanics. Volume 873(2019)
• Page Start: 942
• Page End: 976
• Publication Date: 2019-08-25
• Subjects: morphological instability, -- solidification/melting, -- turbulent boundary layers; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2019.398
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : Ice scallops are a small-scale (5–20 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 15 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.