Hi,
I am simulating a Helmholtz equation (using the PDE mode module) with a Neumann boundary condition. Some days ago, we decided to update our Comsol version from 3.4 to 4.0. In the new version we saw a few changes about the definition of Neumann boundary condition (now called flux/source condition):
While in the older version the equation was:
n•(c?u)+qu=g
in the actual one it is:
-n•(-c?u-?u+?)=g
Does anyone know if both equations are equivalent?
I have been reading the documentation I have (modeling guide for both versions) but I did not find out any clue.
Besides, for the older version I realised that although in the manual it is said that Neumann equation is
n•(c?u+?u-?)+qu=g-h^T ?
the program interface only shows n•(c?u)+qu=g.
I do not think both equations are the same. I am trying to understand why the definition of the manual does not correspond to the equation shown in the program (when using Helmholtz PDE).
I would be very pleased if someone give me any idea about this topic.
Thank you very much,
Cristina