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I need to couple two different domains defined by different physics:

1. In one of the phases the quantities u_s, v_s (which do not represent deformation) are governed by a set of differential equations similar to the Elasticity equation.

2. In the second phase, the variables u,v,p (similar to x velocity, y velocity and pressure) are governed by the Stokes Flow equation. (This includes a forcing term somewhere in the fluid domain which is easy to add).

3. On their common boundary, the stresses should be equal (stress from fluid.normal vector=stress from solid.normal vector) and u and v should be equal to 0 (because no slip and steady state).

I need to solve this problem for steady state. I am new to comsol and I know how to solve each of these problems individually, but I dont know how to couple these two. Do note that they are just derived from elasticity and stokes flow and so no actual deformation is taking place.

Another problem here is that the circular solid inclusions are completely immersed inside the fluid and therefore there is no way to add a dirichlet boundary conditions. I am only concerned with averages inside the fluid phase so the values in solid phase dont concern me directly.