# transport equation

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 July 7, 2004, 09:49 transport equation #1 CMB Guest   Posts: n/a Hi, I am trying to model an electrochemical device with v3.15. In order to achieve a conservation of charge I have to define a different continuity equation for the potential distribution inside a solid region (i.e. domain of solid cells). The potential does not follow traditional d/dxi (roi ui) = 0 but (d/dxi)^2 (poti) = 0, (i being the x,y,z, ro density, u being u,v,w and pot the potential) this is Laplace's equation. Is it possible to apply this in Star?, As far as I am concerned sormom.f allows you to modify the momentum equation but what about the continuity equation for conduction in a solid block? Would appreciate any suggestions. Many thanks, CMB

 July 8, 2004, 03:36 Re: transport equation #2 Richard Guest   Posts: n/a You can only solve for temperature in solid materials. I presume you are modelling your solids using a fluid material but with momentum deactivated? I think that's what you'd need to do. Then, you can model your potential as a passive scalar and choose "diffusion" as the solution method for it. This will deactivate the convection term completely (although you will already have zero velocity through having deactivated momentum, so it might not make much difference).

 July 9, 2004, 05:19 Re: transport equation #3 CMB Guest   Posts: n/a Yes, I see what you mean. It will not make much difference. But how about setting my solid region as a porous one, with a very very low permeability?, that way I can still keep momentum activated and as you say solving for diffusion in this particular scalar?, I think I will do this. Best Regards, CMB