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Species transport without reaction

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Old   May 1, 2014, 06:25
Default Species transport without reaction
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prince
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Dear Friends

I am trying to simulate a simple problem of species transport without reaction and wanted to observe the concentration profile at outlet and in the whole domain.

Geometry is like this. There is long cylindrical pipe with inner obstruction to flow. Obstruction i have modeled as wall and there is no flow across them. The fluid domain is mixture of argon gas and deuterium gas. Argon gas inlet is provided from the side (680 mm below the top of pipe) and Deuterium inlet is from the bottom of pipe. Outlet is at 45 mm below the top of pipe.

I have switched on species transport model. In that i did check inlet diffusion box along with diffusion energy source. No reaction is involved.

I defined mixture-template (Argon-Deuterium) in mixture material. Argon as main component is kept at bottom in the mixture list.

Boundary condition:- Argon inlet velocity (1.35 m/s) & Deuterium inlet velocity (1e-06 m/s). Mole fraction of Deuterium at Argon inlet is specified at 0 and Mole fraction of Deuterium at deuterium inlet is 1.0.
At outlet pressure boundary condition is applied.

Default values of Operating condition was kept. First order upwind scheme was used. The problem was simulated and convergence was also good.

Problem i am facing is this.
1) I am observing more deuterium at outlet than it is coming in ?

What i am doing wrong.
Sorry for log message..
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Old   May 1, 2014, 17:25
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François Grégoire
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Hi,

How much more?
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Old   May 2, 2014, 08:19
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prince
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Hii Macfly

Thanks for responding

If i performs mass balance on deuterium, outlet comes out 10 times more than inlet. Although my problem is converged (continuity order of 10^-12).
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Old   May 2, 2014, 08:39
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François Grégoire
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Hard to say...

Did you try to refine the mesh, second order schemes? Is it transient or steady.
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Old   May 5, 2014, 00:48
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prince
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Hii

I did try all that..
Its a steady state problem

Problem seems very simple..
I know i am doing one very silly mistake.
I just not able to indentify it..
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Old   May 5, 2014, 07:14
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François Grégoire
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How is the Mass Flow Rate balance in the Flux Reports? Is the overall mass balance ok?
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Old   May 6, 2014, 02:02
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Hii

Thanks again for your help.

Overall mass balance is good.
I get convergence of order of 10^-11 or so for overall mass balance.
I am still stuck at same place.
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