Discussion Forum

Hello COMSOL community

I'm am trying to integrate the KdV equation with a moving BC using the "General Form PDE" Interface. I basically implemented the equation the same way it was shown in the COMSOL help/ tutorial. Now I want the left BC's x-position (x_g) to be changed over time. Ideally its movement should depend on the form of the incoming solitons/ waves. Moreover the solution's value at the boundary depends on its x-position (Dirichlet BC: R[x _g(t)] ). Does someone know a way how to implement such a model in COMSOL?


The idea behind this can be pictured as a diverging channel which ends in a lake and according to the incoming waves' form and speed, the point where the channel "ends" and the lake "begins" should be moving. This is an artificial model though. Most important is the moving boundary and its dependency on the KdV solution.


It should look like this:

t1:
//////////////////////////////
/////////////////////////// <- , ’’,
////////////////////////~~~’’’’’’’~~~~
////////////////////
..CHANNEL | FREE SURFACE

t2:
//////////////////////////////
/////////////////////////// ’’,
////////////////////////’’’’’’’’~~~~~~~~
////////////////////
......CHANNEL | FREE SURFACE




Thanks for your help!