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Hello,

I am using Comsol Multiphysics 3.5a. I am modeling a problem involving three models, Solid Stress-Strain (including thermal expansion), PDE General Form and Moving Mesh (ALE). My geometry (2D) has two concentric circles of 1 m and 0.6 m. My problem involves pahse changing material. Assume that the outer cicle is made of phase beta and the inner circle of phase alpha. Now, say, the depending variable for the PDE model is c, which is concentration. 'c' is also used here as the depending variable for thermal expansion, which means instead of T, I'm using c. Basically, using a thermal analogy for diffusion induced stresses. I have a definite flux coming in from the outer boundary, and as the concentration near the boundary of the inner circle increases, it starts converting from alpha phase into beta phase. With this, the inner boundary/circle starts shrinking towards the centre with time. For this moving inner boundary I need to use the moving mesh technique.

I have an equation defining the velocity of this inner boundary, which depends on the concentration on both sides of the boundary. Can anybody help me model it? I have been trying it myself, but to no avail. I'll be really thankful if you can help in any way.