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FloEFD - Radial Blower

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Old   July 31, 2015, 06:10
Question FloEFD - Radial Blower
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Markus
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Hi Folks,

first I should admit that I'm quite unexperienced in dealing with FloEFD (CATIA V5 Environment).

I'm trying to simulate the airflow of a radial blower with Stator housing & a short duct.
I'm running 'external' simulation. I've set the housings as 'ideal wall' and the impeller as 'real wall' with rotating condition.
The intake and exhaust lids get primary conditions 'environmental pressure'.
(besides a question to the developers: would it be possible to integrate visibility of the direction of rotation also on moving wall feature?)

Several attempts using a rotating region instead have lead to strange results.

Leaving the rotating region out (what seems more correct to me) leads to "Maximum mach number exceeded" what I cant explain to myself...
Im running the blower at 4100 rpm - I entered 420 rad/s. 4100 rpm on the other hand would mean that I have a circumferential Speed of about 15 m/s (what is intended to have).

Could it result out of the low gridding I entered the first simulation runs with.
Or do I possibly have a mistake in my simulation setup?

~bit confused~

Thanks for your help,
BR

Last edited by Suppengruen; July 31, 2015 at 08:44.
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Old   August 6, 2015, 03:40
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Hi Suppengruen,

You should use the rotating region approach as the rotating walls are only applying a moving boundary condition onto the surfaces but not actually a rotating impeller blade. This should also give bad results as it is absolutely not correct regarding the physics you want to simulate.
By the way, the rotating direction is indicated in some way. Try to hide the geometry while you are in the boundary condition with the rotating walls activated. You will see the rotating vector and as usual the right hand rule is the key if the rotation direction is not indicated like in the rotating region feature.

To learn more about the way to setup the rotating region you should have a look at the PC fan tutorial and the technical references that come with the software. There is a PDF installed and you can find it in the start menu under the English documentation of the FloEFD folder there.

Yes, that might be due to too coarse mesh or just a single bad cell that causes that error. Use the plots to find that location and fix it by adding another cell in either one of the main coordinate axes. This will shift the cell slightly and usually fix it already.
You can use the Display Global Min and Max values option which show a small sphere at the location of the current visualization parameter you have active. You might need to show a cut plot or so to have a visualization active and a parameter for that.
If you use the plot without interpolation it show you very nicely the very "red" (high velocities) and right next to it already very low velocities.

Regards,
Boris
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