On Feb 21, 2022, at 7:48 PM, 'Guyer, Jonathan E. Dr. (Fed)' via fipy <[email protected]<mailto:[email protected]>> wrote:
On Feb 20, 2022, at 2:23 AM, Matan Mussel <[email protected]<mailto:[email protected]>> wrote: I started examining this version of the code. I am still wondering about the equations since after ~500dt the circle takes an octagonal shape, and after ~1100dt the solution diverges. I'll try to use parameters with a known solution. Since the solutions I know of were solved in cylindrical coordinates, I'll try first to convert the code to work with a cylindrical grid. I haven’t observed either, but maybe I didn’t run long enough. The octagonal symmetry doesn’t surprise me; it’s almost certainly “feeling” the edges of the mesh. OK, I ran longer and see what you mean. I still think the octagonal symmetry is arising because of the box size. As to the divergence, I’m only guessing, but there are three length scales in your equations: - one associated with the terms 2nd-order in \phi. This is the \tanh solution that describes the diffuse interface. This length is of order \epsilon. - one associated with the 4th-order term in \phi. I’m not positive, but I think this one may be order \epsilon, too. - one associated with the term(s) in sigma and phi. It’s this one that I’m guessing is the issue. As the problem destabilizes, you can see undulations in \xi along the interface as sigma gets large. My guess is that one or more of these length scales is under-resolved. The paper says that \sigma is small and essentially homogeneous, but they never quantify it. -- To unsubscribe from this group, send email to [email protected] View this message at https://list.nist.gov/fipy --- To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
