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Logarithmic transform in a time dependent diffusion equation
Posted Jan 23, 2011, 11:21 PM EST Materials, Parameters, Variables, & Functions, Studies & Solvers Version 3.5a 3 Replies
I have been trying to avoid negative concentration by incorporating logarithmic transform of concentration. The knowledge base tells us how to do this in a stationary problem ( www.comsol.com/support/knowledgebase/952/ ). However when there is a time dependent equation, the term dc/dt in the log transformed state becomes exp(C) dC/dt, where C=log(c) . How do i incorporate exp(C) as the coefficient to dc/dt. I tried using general form pde and input the coefficient of dC/dt as exp(C), but it says failed to find consistent initial values. Is there a way around this or a better way to incorporate log transform?