Computational Modeling of Close-Contact Melting Processes


It is now widely accepted that the presence of liquid water on planets and moons of our Solar System bears some potential for the development of extraterrestrial life. One candidate is the Saturnian moon Enceladus. At Enceladus' South Polar Terrain, ice grains that contain organic compounds are ejected into space. They originate from a subsurface ocean and have been transported through a 30-40 km thick ice layer via cracks. These cracks could serve as potential access points for the exploration of subglacial aquatic ecosystems at moderate depth and eventually for the search for life. In view of future missions, various innovative melting technologies for autonomous and/or maneuverable motion through the ice have been proposed. This also requires advanced simulation technologies tailored to assess, evaluate and extrapolate the dynamic range of the proposed melters. From a mathematical modeling perspective these concepts can be phrased in terms of a close-contact melting (CCM) situation, in which a system of partial differential equations describes multi-phase processes within the micro-scale, liquid melt, beyond the phase  interface in the solid ice, and along the melting channel where refreezing has to be taken into account. Even though, we primarily focus on modeling melting probes, CCM is not restricted to the field of glacier ice exploration, but can be found in a variety of other fields, e.g. thermal energy storage, nuclear or manufacturing technologies.
Instead of using analytical solutions, which are already existing for some simple geometries, our objective is to develop a
computational model that can predict the trajectory of a heat source having an arbitrary geometry that melts into a phase change material due to an imposed force and a certain heat distribution. Since one of the main fields of application for such a model is the shape and trajectory optimization of melting probes, the model should both work for terrestrial, as well as for extraterrestrial environments (melting probes for space exploration), i.e. depending on the ambient pressure, sublimation needs to be considered in the model.