Transport near a vertical ice surface melting in saline water: experiments at low salinities

Abstract

Time-exposure photographs of the buoyancy-driven flow adjacent to a submerged vertical ice surface melting in 10‰ saline water are presented for ambient water temperatures between 1 and 15°C. For ambient temperatures greater than 1·9°C, the thermal and saline components of the buoyancy force are at least partially opposed to each other. Since most past studies of ice melting in saline water have concentrated on oceanic salinities, little is known about the complicated flow behaviour which results from these opposed buoyancy effects at ambient water salinities between fresh water and oceanic salinities (35‰).The results presented here provide new insight concerning the subtle mechanisms which arise in such flows. Photographs of the entire flow field document the many different and complicated flow configurations that arise. At 10‰, as the ambient temperature is increased from 1 to 15°C, regimes of upward, bi-directional and split flow are observed. In the latter circumstance, the flow is laminar and bi-directional over part of the ice surface and turbulent over the rest of the surface. Bi-directional flow results from reversal of part of the upward wake above the top of the ice surface. Split flow appears to be a consequence of the transition to turbulence of either the inner or outer portion of the laminar bi-directional flow. Measured velocity profiles, surface heat-transfer rates and interface temperatures agree well with the analytical results reported in a previous study for conditions that result in conventional boundary-layer flow. These experimental results, together with those of previous studies, indicate the approximate extent of the different flow regimes that arise for a vertical ice surface melting in cold, low-salinity water.