A coupled heat-and fluid-flow model to study the initial contact between a melt and a water-cooled substrate (belt) is presented. The key elements of the model are the fluid flow and heat transfer of the molten metal (including phase change), waterside cooling, intervening moving metal substrate, and a gas layer generated by an active interfacial "contact" layer. A unique aspect of this article is the introduction of a subgrid model for the description of the contact-layer heat transfer in the initial melt/substrate contact region. The subgrid model, developed around multiphase conservation equations and an Arrhenius reaction model, is incorporated within the framework of macroscopic equations for heat and fluid flow applied to a computational grid much larger than the scale of the contact layer. The model results are compared against experimental casting data, and the predictions are assessed with a view to understanding surface cooling conditions and the impact on surface metallurgy in strip casting of thin-gage product.

SUMMARYA large number of industrial surface coating and continuous casting operations require a fluid to flow from a reservoir, over a compliant step, onto a moving substrate. The contact line between the compliant step and substrate in such cases generally responds in an unsteady manner, depending on flow conditions, which can have an important influence on the surface quality of the final product. This work describes the development of a computational fluid dynamics (CFD) model for predicting this unsteady response, with a particular emphasis on isolating the natural frequency of the contact line in a backward-facing step configuration. The compliant step was developed and implemented in the context of a pressure-based finite-element/finite-volume CFD solution, implicit in time, and considers in-surface forces based on a surface tension coefficient or an elastic membrane.