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Old   July 12, 2001, 10:09
Default about two-wall boundary
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Mark
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Hi,

I have a problem about two-wall boundary.Now I simulate combustion of gas.I choose eddy-dissipation, 2-eqs turblant flow.

The wall zone has a fluid or solid region on each side. I would choose coupled option under Thermal Conditionsto to couple the two zones.

When I define one species mass fraction on two-wall boundary as value 1,the solver cannot continue to solve it after a few iterations.

When I define one species mass fraction on two-wall boundary as zero disffusive flux,it can get a result.But the temperature is too much high(about 5000K).

How can I solve it?Would you give me some advice?

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Old   July 12, 2001, 20:53
Default Re: about two-wall boundary
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Greg Perkins
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What is the physical significance of having a constant species mass fraction at the wall??

To me, this implies the potential for a diffusional flux between the wall and the adjacent fluid cell due to a difference in concentration. This may or not be a good model for your problem - it depends.

If you want a standard wall then the zero diffusional flux is appropriate. The high temps are probably a sign of something else - check heat transfer boundary conditions, diffusion vs convection heat transport and reaction scheme. Overall either too much heat is being generated or the heat generated can't be dissipated quickly enough from the reaction zone (or both)

Greg
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Old   July 12, 2001, 21:21
Default Re: about two-wall boundary
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Mark
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Hi,

Thank you.

I am simulating a kind of species added into fluid from "two-wall" boundary.So I define this species mass fractionn as value 1.After I get a good cold flow,I simulate gas of combustion.But after 500 or so iterations,there is error message and the solve can not continue to solve, and the solver didn't reduce the CFL.

I don't how to solve it.Thank you.
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