Session: 7.9 - Multiphase flows in Environmental and Industrial applications

Paper Number: 158657

158657 - Morphodynamics of Melting Ice Over Turbulent Warm Water Streams 

Abstract: 

The morphodynamics of ice melting over warm water currents is characterized by complicated interface patterns commonly observed under ice shelves that depend on the flow velocity. Since these features can affect the interfacial heat transfer, a precise appraisal of these phenomena, which is not fully addressed in most ice melting models, has major implications for quantifying global melt rates. We investigate ice morphodynamics using direct numerical simulations of Navier-Stokes and energy equations, coupled with a phase field method and an immersed boundary method in an open channel configuration. Through extremely accurate simulations at different Reynolds numbers and Stefan numbers, we provide a sound characterization of the melting/freezing phenomena that shape the ice–water interface, revealing new insights into the mechanisms that control the interface morphodynamics. At low Reynolds number, streamwise undulations appear that can be linked to the near-wall turbulent streaks. As Reynolds number increases, these undulations combine with spanwise ripples of much greater length scale. These ripples are generated by a melting mechanism controlled by the instability originating from the ice-water interactions. Through a melting/freezing process, ripples evolve downstream with a migration velocity much slower than the turbulence characteristic velocity. This morphodynamic instability is due to a relative phase lag between the shear and heat flux at the ice-water interface. Our results demonstrate that the combined melting and freezing mechanisms triggered by turbulence and the morphodynamic instability cannot be explained by the Reynolds analogy, due to the occurrence of a phase shift between the local heat transfer and the local momentum transfer. We have been able to establish a causal relationship between the phase shift and the anomalies in pressure distribution and turbulent convection that are induced by the surface morphology. Considering the pivotal role played by melting and freezing in ice loss beneath ice shelves, we believe that our findings enhance the current understanding of ocean circulation within ice-shelf cavities and lay the groundwork for refining physicsbased, geometry-dependent parameterizations of the melting process in large-scale ocean circulation models.

Presenting Author: Cristian Marchioli University of Udine

Presenting Author Biography: