Mass transport simulation
 

Hi
Would appreciate some help with mass transport issue.
I would like to perform a 2D density driven flow simulation (haven't decided on the CFD platform yet). The system involves a fully miscible, less dense then water, solution which sits on top of water. The miscible solution diffuses into the water (i assume thermodynamic equlibrium which means that the dissolution rate is governed by diffusion) causing the water under the interface to become denser thus forming an unstable condition followed by natural convection. I'm trying to define the boundary condition at the interface (assuming its location is fixed) but i cannot define it as a species that is dissolved in water because it is still "pure".

Any ideas?

Thanks!

which software we are talking about?

It is likely i will use comsol for this

I don't know much about comsol but in fluent starccm etc you can patch the value to a region as initialization. Off course then you would have to make two regions, one for one fluid another for another fluid.

In FVUS/Wildkatze , I provide patching in a box or sphere because of this, so there you can use your mesh the way it is, just create a box patch where the values will be fixed to what you want.

For example here , the column of water is from patching in a box and mesh is single region mesh

https://www.youtube.com/watch?v=dGMN_OeuO24