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step function in diffusion equation

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Hello,

Can anybody help me !! I am solving diffusion equation in 2D geometry, initial concentration in domain = 0, I gave Dirchlet boundary condition with some constant number. I am trying to look at the phenomenon of stuff diffusing into the geometry. When I solve I see some negative values for first few seconds and read that it can be corrected using STEP FUNCTION.
Please can anyone tell me how to implement step function in V4.2a!

Regards
Harkirat

0 Replies Last Post 2012年5月21日 GMT-4 16:21
COMSOL Moderator

Hello Harkirat Bansal

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