Flow-induced traveling waves on solidification interfaces

We address the dynamics of the solid/liquid interface of a solidifying material when the liquid phase is flowing with respect to the solid phase. To visualize the interface and independently control both the flow and the solidification conditions, we use a thin sample filled with a transparent melt. Whereas this set-up involves no flow by itself, we link it to a thermosiphon which provides an external flow source for the liquid phase. We then evidence a new instability of solid/liquid interfaces which emerges from the coupling between solidification and flow. It is oscillatory and generates two kinds of traveling waves on the interfaces. Both waves periodically modify the growth conditions of the solid phase yielding bands of composition in the solidified material. This instability is expected to widely occur in freezing media due to the usual natural occurrence of thermal or thermosolutal convective flows in their liquid phase. Copyright (C) EPLA, 2013