# A coupled problem with different equations in different geometries

 Register Blogs Members List Search Today's Posts Mark Forums Read

 September 6, 2018, 13:23 A coupled problem with different equations in different geometries #1 Member   Wenming Yang Join Date: Jun 2018 Posts: 42 Rep Power: 5 Hi, I am solving a problem consisting of two coupled equaitons. These two equations are solved in two adjacent geometries, respectivley. Coupling takes place at the interface between them and the interface moves according to the solutions of the equations. Some kind Foamers advised using dynamic mesh and it can deal with one equation in one geometry. But how can I deal with the case when two different equations concern on different geometries. Dose anyone has some ideas about the method to solve this problem using OpenFOAM? Many thanks.

 September 7, 2018, 04:29 #2 Senior Member   Michael Alletto Join Date: Jun 2018 Location: Bremen Posts: 544 Rep Power: 10 The are also dynamic mesh and overset mesh technologies available for the volume of fluid method. Maybe this helps

 September 7, 2018, 05:48 #3 Senior Member   anonymous Join Date: Jan 2016 Posts: 417 Rep Power: 11 Just some ideas, maybe helps, maybe just ignore them: 1, What if you use the interFoam for a base, but use the alpha to blend the equations? I'm not sure if it is possible, but I think it is. Something like: eqn1 = "dummy stuff"; eqn2 = "dummy stuff"; Solve ( alpha*eqn1 + (1-alpha)*eqn2 == 0 ); The problem with this is to figure out the equation which will change the alpha field, and maybe at the interface there will be some weird stuff... 2, Or you can check the chtMultiRegionFoam solver. This solver is for two types of regions (solids, and fluids). But you can rewrite it as you wish. You can define the equations for each type of regions, where each region has it's own geometry (mesh). The communication between them is done with a coupled boundary condition, but maybe you will have to write your own BC for your problem, and you can also add the dynamicMesh functionality to it.

 September 7, 2018, 11:30 #4 Member   Wenming Yang Join Date: Jun 2018 Posts: 42 Rep Power: 5 Dear Alletto and simrego, Thank you very much for both of the suggestions. Hopefully they will work. Best wishes,

 Tags different geometries, equations