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wrong definition of a fluid?

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Old   January 25, 2011, 08:10
Default wrong definition of a fluid?
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Hi,

I am currently simulating with a special cooling oil, which I defined in CFX as material. I set density and dynamic visocity (which are the only values available for me). When I try to simulate the flow, I get the following error:

ERROR #002100004 has occurred in subroutine Out_Scales_Flu. |
| Message: |
| The Reynolds number is outside of the range expected based on the |
| Option selected for the TURBULENCE MODEL. Check this setting, |
| the values of the properties, mesh scale, consistency of units |
| and solution values in the input file. Execution will proceed.

When simulating with water, everything works without any problems.
I tried k-epsilon and SSG turbulence model.

Does anybody of you have a suggestion how to make this error disapear?

stefank
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Old   January 25, 2011, 08:30
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It's just a warning, since it says "Execution will proceed."

I would guess that be that your values for density and viscosity made the Reynolds number much lower (laminar?), and that you shouldnt use a turbulence model when simulating with your own material.
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Old   January 25, 2011, 08:37
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Thank you for replying!

I will try without turbulence now. I was just wondering, because the simulation with water takes around 12 hours and the one with my own material around half an hour. And at the end the solver does not produce a result file.
But we will see what's coming with the laminar model.
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Old   January 25, 2011, 17:08
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You should work out a representative Reynolds number and see whether it is likely to be laminar. That is what tells you whether you need a turbulence model or not.

What is the Re number using water and using your fluid?
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Old   January 25, 2011, 17:56
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Yes, you are totally right!

It did not thought about the step calculating the Re number before running the simulation. With water I got 7700 and with my fluid I got 640. I did not assume that there is such a big difference in the Reynolds numbers. So definitly this is the point why it did not work. Currently the simulation is running without an error and I hope to get some results tomorrow in the morning.
Thanks for replying!
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Old   January 26, 2011, 10:36
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hi

I just got results after 25 hours of calculating, and they don't make sense at all! I set the same setting as I used in the simulation with water. (Apart from the turbulence model) I used laminar flow for this case.
The following pictures show the result on a cutting plane.

First picture: water
Second picture: own fluid
wasser_plane1.jpg
atf_plane1.jpg

The results must be wrong, not even the no slip conditions on the walls are adopted. (The body at the top is staionary, and the body at the bottom has a rotational velocity defined). Do you have any suggestions where I could find the mistake?
I am looking forward to get some hints!
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Old   January 26, 2011, 11:32
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Sorry guys, problem solved! I used a wrong scale in the legend.
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Old   February 2, 2011, 04:42
Default same error
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hi
I have the same error when I run my simulation however I have one fluid(air) but the flow change its direction from striaght at inlets to swirling inside my chamber...How I can manage my flow on other words how I can now when the flow change from laminar to turbulent. by the way I calculate my Re and it is turbulent...
It seems to me tricky error?
I try to change the flow to laminar by decreasing the velocity, but the same error appear inversily????
help pls to disappear this error
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Old   February 2, 2011, 06:23
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If you are referring to "The Reynolds Number is outside..." error - then don't. It is really a warning and the simulation will continue. But it is up to the user to decide whether to heed the warning.
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