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fluid flux with dilute species model

Posted 6 oct. 2014, 22:27 UTC−4 Fluid & Heat Version 4.2, Version 4.2a 3 Replies

John Kim
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Hey all,

I'm sure this has been beaten to death, but I cannot seem to make a simple fluid flux across an arbitrary boundary work. My model consists of a container with a fixed amount of solute, and a C=0 boundary on one side. How do I get ahold of the normal variable names to generate a surface integration along a boundary of my choice? I can make a cut line or cut plane, but I don't see a way to get the plot I need.

Thanks,

John
3 Replies Last Post 7 oct. 2014, 14:20 UTC−4
Lasse Murtomäki
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Posted: 1 decade ago 7 oct. 2014, 01:48 UTC−4
You mean the convection across a particular cut plane? If the model is 3D, the velocity components are u,v, and w. Just integrate u+v+w across the plane.

If the flux is diffusive, integrate D*(cx+cy+cz) where D is the diffusion coefficient and c is the concentration of the diffusing species. It is true, as you said, that using the internal Comsol variables produces an ambiguous error message, but the latter worked for me, at least.

You mean the convection across a particular cut plane? If the model is 3D, the velocity components are u,v, and w. Just integrate u+v+w across the plane. If the flux is diffusive, integrate D*(cx+cy+cz) where D is the diffusion coefficient and c is the concentration of the diffusing species. It is true, as you said, that using the internal Comsol variables produces an ambiguous error message, but the latter worked for me, at least.
John Kim
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Posted: 1 decade ago 7 oct. 2014, 14:13 UTC−4
Thanks. No, I just want diffusive flux for this model.

What I ended up doing was just taking a surface integration (under derived values) using the default expression for total flux magnitude, at a cut plane of my choice I established after solution. This gives me a flux at each time point... for total flux for a given time span, I suppose I just sum these together?
Thanks. No, I just want diffusive flux for this model. What I ended up doing was just taking a surface integration (under derived values) using the default expression for total flux magnitude, at a cut plane of my choice I established after solution. This gives me a flux at each time point... for total flux for a given time span, I suppose I just sum these together?
Lasse Murtomäki
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Posted: 1 decade ago 7 oct. 2014, 14:20 UTC−4
I understood that you wished exactly that, flux across a predefined cut-plane.
I understood that you wished exactly that, flux across a predefined cut-plane.

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