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January 8, 2008, 02:45 |
surface exchange b.c.
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#1 |
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I have done a number of models with the built in physics modes of Comsol 3.3 Now I need a special bc that's not builtin and need some advice.
For a 1-d model, the bc (boundary condition) is for diffusion flux determined by a surface exchange coefficient: j=k (c1-c2*B) where j is the flux (=-Ddc/dx on left and right of the boundary) k is const c1 is concentration on left of boundary c2 is concentration on right of boundary B is const I thought of exploiting the builtin boundary equations where one has n(N1-N2)=N0+k(cb-c) and setting cb appropriately, but this isnt right as my bc is still conservative (what flows out of one side flows into the next) so n(N1-N2)=0. The boundary concentrations are apparently available thru the 'up' and 'down' functions to access the values of c just before and after a boundary , how do i define a bc to use these? Do I need to use 'weak form' if I only want to set the tangential derivative j=k (c1-c2*B)=-D dc/dx Also is there a spherical symmetry model setup? |
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