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March 4, 2012, 02:23 |
Imporatnt questions
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#1 |
Senior Member
Safia
Join Date: Oct 2010
Location: Australia
Posts: 161
Rep Power: 15 |
Hi there,,,
I have question about the way of using the models into CFX. For example, if I need to use K-epcilon turbulent model, I'm always thinking that if I did not tick any square in the path (Domain:.../Fluidmodel/any parameter.....) mean that the program will use the default setting? is this right). As well as, for the same model and regarding the eddy diffusivety, if I did not tick it, the program will calculated and if I tick it, it means that I should insert a value. is this either correct? Please, answer my question as soon as possible where I misrecognise these things. Regards |
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March 4, 2012, 04:01 |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
K-epsilon turbulence model is the default.
Where are you saying you tick eddy diffusivity? |
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March 4, 2012, 05:01 |
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#3 |
Senior Member
Safia
Join Date: Oct 2010
Location: Australia
Posts: 161
Rep Power: 15 |
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March 4, 2012, 05:06 |
share us youe knowledge
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#4 |
Senior Member
Safia
Join Date: Oct 2010
Location: Australia
Posts: 161
Rep Power: 15 |
Hi Glenn
By the way, you did not answer my question into your first input??tell me if you are still confusing Regards |
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March 4, 2012, 16:38 |
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#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
The default when you set up a fluid domain is that it has the k-e turbulence model applied.
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March 5, 2012, 01:05 |
still need answers
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#6 | |
Senior Member
Safia
Join Date: Oct 2010
Location: Australia
Posts: 161
Rep Power: 15 |
Quote:
If you understand me, please answer my previous questions and next one,,, Is is important to inter specific value for eddy viscosity. and if I did not tick it, will the progaram calculate it? Regards Last edited by happy; March 5, 2012 at 04:06. |
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March 5, 2012, 05:36 |
no one know
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#7 |
Senior Member
Safia
Join Date: Oct 2010
Location: Australia
Posts: 161
Rep Power: 15 |
It looks no one know
it is easy w.r.t Glenn and some guests. I want to make sure help me please. |
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March 5, 2012, 05:43 |
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#8 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
I do not use 3rd party download tools so have not seen your attachment. Please attach it to the forum.
I do not understand your previous question beyond what I have already said, you will have to write it more clearly. Your question about entering eddy viscosity is vague - where are you entering this? |
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March 5, 2012, 18:03 |
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#9 |
Senior Member
Erik
Join Date: Feb 2011
Location: Earth (Land portion)
Posts: 1,167
Rep Power: 23 |
I think he is saying where you can choose to enter a value for something or not, like when you can mark the checkbox that reads Turbulent Flux closure for heat transfer, then an option comes up to Turbulent Prandtl number, the box is already populated with 0.9.
Same thing with Buoyancy turbulence, you can check mark a box for turbulent schmidt number, which then allows you to input a value, which is already populated with 0.9. He is asking are these already set to 0.9 even if you don't check the box, or if the program will just calculate a value if we don't check these boxes? I'm under the impression they are 0.9 by default, because i did not see an equation for calculating them in the solver theory guide, though i may have missed it. |
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March 12, 2012, 01:30 |
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#10 |
Senior Member
Safia
Join Date: Oct 2010
Location: Australia
Posts: 161
Rep Power: 15 |
hi Erik
you are compeletly understand me. yes, that what i meant. regards |
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March 12, 2012, 04:24 |
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#11 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,703
Rep Power: 143 |
The Schmidt number of 0.9 is one of several turbulence model constants. It is empirically tuned to match experimental data, it has not been theoretically derived. That is why it is called a turbulence MODEL, not a turbulence THEORY.
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