Discussion Forum

Dear friends

I simulate one-dimensional problem of heat propagation with a phase transition. For example, it could be the problem of crystallization of amorphous ice.

The computational domain consists of two parts with different characteristics. At the initial state the size of the first sub-area of ??x1 and the second - x2. At the inner boundary there is an energy release (I use the condition of discontinuity of the heat flow).

The left external b1 and internal b2 boundaries move with velocities V1 and V2, respectively. The displacement of the outer boundary is caused for example by evaporation, and the motion of the internal boundary - by the propagation of the crystallisation front. Velocities are different! I use the ALE module to describe the moving boundaries. I expect that if the velocity of the left (outer) boundary is V1, and the velocity of the inner is V2, and V2> V1, the region x1 increases with time (internal boundary moves faster!). However, test calculations (where I explicitly specified that V1 <V2) show that the outer boundary moves faster!, and domain x1 disappears and simulation terminates at some time.

Now the actual question: how to specify the motion of two boundaries (one internal ) with different velocities?

Thank for support and ideas

Yus