Definition of Concentration Diffusivity

Numerical methods and mathematical models of Elmer
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Gary R
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Definition of Concentration Diffusivity

Post by Gary R »

I'm having trouble with the setup on the Advection Diffusion Solver. I used mass concentrations through out. It insists that Concentration Diffusivity (CD) is missing. Is Concentration Diffusivity and Diffusion Coefficient the same thing. If not how do I find the CD value. I've had a pretty good background in theoretical Physics but the diffusion area (Ficks Law for instance ) eludes me.

Gary R
Rich_B
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Joined: 24 Aug 2009, 20:18

Re: Definition of Concentration Diffusivity

Post by Rich_B »

Hello,

Take a look at the Electrokinetics tutorial, it includes the keyword Concentration Diffusivity. From looking at some literature articles, CD and DC are the same.

Rich.
mika
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Re: Definition of Concentration Diffusivity

Post by mika »

It seems that the advection-diffusion solver reads the diffusion coefficient from the keyword command in the form

my_solver_variable Diffusivity = Real ...

where the part "my_solver_variable" should be the string which is used as the value of the solver variable. That is, the command

Concentration Diffusivity = Real ...

works only when the solver variable is "Concentration".

-- Mika
raback
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Re: Definition of Concentration Diffusivity

Post by raback »

The reason for this is that while usually there is only one Navier-Stokes or Heat equation there can be a number of transport equation. Think of transport of different chemicals, for example. Each of them with different sources, diffusion coefficients etc. -Peter
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