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weak mode boundary form

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I am modelling the growth and collapse of a gas bubble due to diffusion.
my boundary condition is cs=H*pg for the diffusion equation but pg is continuously changing due to the diffusion too according to the equation:

d/dt(pg*V/RT) = area*D*dC/dr

on the boundary. my problem is that i want to express in the weak form the above equation but i have two derivative one with respect with time and the other with respect to radius of two different dependent variables.

How can I write it?

Thanks a lot guys

0 Replies Last Post Sep 22, 2009, 7:19 p.m. EDT
COMSOL Moderator

Hello cecilia borgonovo

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