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PDE boundary conditions

Posted 16 mars 2012, 20:16 UTC−4 Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2a 0 Replies

Matthias Weiland
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I am trying to model water absorption/desorption in a polymer (d1) through an adjacent boundary domain (d2) through a PDE. The absorption and desorption rates (rab & rdes) are specified in relation to an equilibrium level l0 (l303). Within a time dependent analysis this equilibrium is increased for a certain period of time and the real level l slowly follows. However, when reaching equilibrium after about 0.7 s and the absorption rate actually drops to zero the real level l still increases although it should level out (the desorption which should result in the opposite lowering the equilibrium level is disabled at the moment).

I cannot figure out, why this is happening. It does not seem to be an issue of the acting diffusion part in the PDE itself, as the level is increasing in both the boundary domain and the pure polymer. As this is the first time I am setting up an own PDE, I am not entirely sure if I miss out on something considering the boundary conditions.

Thanks a lot,
Matthias

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0 Replies Last Post 16 mars 2012, 20:16 UTC−4
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