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Natural convection of in gas-gas system

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Old   January 5, 2003, 21:08
Default Natural convection of in gas-gas system
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yee wan
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Hi people there! Do anyone tried to simulate the natural convection phenomena in gas-gas system (by diffusion) using FLUENT??

I am wondering wether FLUENT can do this or not??

If anyone has been done it sucessfully, pls share with me how do u setup the things.. By now i am using the species transport model...

Thanks in advance...

YW

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Old   January 13, 2003, 19:17
Default Re: Natural convection of in gas-gas system
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Greg Perkins
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I had a look at this a bit - but was mainly concerned with convection due to temperature gradients rather than concentration gradients. I found no major problems - just tern on the species model, activate gravity, and either use a steady or transient solver depending on the flow regime (Ra number).

When you say natural convection by diffusion I assume you mean driven by changes in the density caused by concentration gradients.

Greg
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Old   January 22, 2003, 04:34
Default Re: Natural convection of in gas-gas system
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yee wan
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Thanks alot Greg, Yes now I am using the species transport for the convection case.

But then do you know how to determine the surface concentration of a defined boundary??

What i do is go to -->report-->surface intergal--> average: molar concentraction... to the the concentraction of the species at the mass flow inlet boundary..

But the value given but FLUENT is much more smaller than the theoritical value I caculated...Do you/anyone know that what actually this concentarction mean?? what volume do the FLUENT refer to in this case?? for me it seem that FLUENT use the total domain volume to calculate the molar concentraction...can anyone give me a solution??

Thankas alot

Tan
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