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boundary condition dependent on dependent variable

Posted Jul 23, 2013, 8:50 a.m. EDT Modeling Tools & Definitions, Parameters, Variables, & Functions 2 Replies

Thomas Hulin
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Hello everybody,

In a coupled heat and mass transfer problem, I would like a pressure BC to get updated at each time step. Let's call this pressure pv.
pv depends on the temperature and pressure (dependent variables solved for in the problem) and the value of pv at the previous time step.

Does anyone have an idea how to implement that in Comsol? Using Matlab is an option.

Thanks a lot for help,
2 Replies Last Post Nov 23, 2016, 12:56 p.m. EST
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Hello Thomas Hulin

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Eric Aerosol Control Technology
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Posted: 8 years ago Nov 22, 2016, 8:33 p.m. EST
Hi Thomas,

Were you able to apply a variable BC?

Thanks.
Hi Thomas, Were you able to apply a variable BC? Thanks.
Mohammad Amin Kazemi
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Posted: 8 years ago Nov 23, 2016, 12:56 p.m. EST
1) Define the variable boundary condition in the variable section, i.e. pv=0.98*p+1.
2) set the boundary condition and insert pv in the pressure field.
3) run the simulation
4) It usually doesn't converge ! :D
5) For convergence issue, I suggest using a ramp function or solving the problem with a constant pressure and using the solution as the initial condition of your main study.
Good luck.
1) Define the variable boundary condition in the variable section, i.e. pv=0.98*p+1. 2) set the boundary condition and insert pv in the pressure field. 3) run the simulation 4) It usually doesn't converge ! :D 5) For convergence issue, I suggest using a ramp function or solving the problem with a constant pressure and using the solution as the initial condition of your main study. Good luck.

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