Hello,

I want to define my own set of PDE and ODE on some domains in COMSOL. Actually, i want to use some predefined equations and some my own equations on certain domains. How can I do that?

Hi,

This is one of the key features in COMSOL Multiphysics: the ability to define your own PDEs as well as ODEs and other "global equations" (algebraic equations, etc.) for equation-based modeling as a complement to the predefined interfaces for fluid flow, diffusion, heat transfer, structural analysis, electromagnetics, etc.

There are three formulations of PDEs that you can use:

- Coefficient form, for linear or almost linear PDEs

- General form, for general nonlinear PDEs

- Weak form, a variational formulation using test functions

The COMSOL Multiphysics Model Library contains a whole section called Equation-Based Models, which is devoted to models that solve custom PDEs using the above formulations. There are also several model examples of how to incorporate ODEs, algebraic equations, etc. Note, though, that such equations are normally space independent and are not defined on a domain.

Hope this helps,

Magnus Ringh COMSOL