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How to set up the runner rotation?

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Old   March 19, 2011, 02:59
Default How to set up the runner rotation?
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Kooky
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Dear All,

I have a mini hydro system that consist of runner and giude vane. I would like to simlulate by using ANSYS CFX. The problem is how to set up the runner rotatation and fix the giude vane (stationary).

Many thanks,

Last edited by Kiat110616; March 19, 2011 at 03:15.
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Old   March 19, 2011, 03:20
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It should be split into three domain: runner domain, fluid domain, and guide vane domain. I have set up the fluid and guide vane domain as stationary and the runner domain as rotation. The results show that the streamline did not go through all domains. How to solve this problem?

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Old   March 20, 2011, 21:57
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Can you post an image?
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Old   March 23, 2011, 09:15
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Meshing of two fluid volume
Meshing.jpg

Set up the boundary condition
- Runner domain is rotated
- Guide vane domain is fixed (stationary)
Setup BC.jpg

Streamline plot
Results.jpg

Is this condition correct?

Last edited by Kiat110616; March 23, 2011 at 09:53.
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Old   March 23, 2011, 18:52
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So what is your question? It looks like the streamlines are going through all domains to me.
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Old   March 23, 2011, 22:29
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I assigned the runner surface to rotate in the fluid domain with stationary condition at inlet, outlet, and fluid wall. The software cannot solve for result. It showed the message " The ANSYS CFX slover exited with return code 1. No results file has been created".

So, I tried to modify fluid domain by separating the guide vane and runner domain as shown in the picture. I'm not sure it is correct because the streamline at interfaces of both domain it should be continuous curve. It should not be sharp. What do you think about that?

Thanks

Last edited by Kiat110616; March 24, 2011 at 10:01.
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Old   March 24, 2011, 09:23
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Quote:
I'm not sure it is correct because the streamline at interfaces of both domain it should be continuous curve. It should not sharp.
It is not all the same that you plot the streamline in stationary or rotating frame: if you can get sharp connections there, because you "loose" the circumferential component.

On the other hand, you have the slice the domain near the inlet and outlet regions of the rotor, so you get 3 domains as you have written above. Did you do so?
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Old   March 24, 2011, 10:06
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"It is not all the same that you plot the streamline in stationary or rotating frame: if you can get sharp connections there, because you "loose" the circumferential component."

I'm a little confused. What do you mean by loose?

Thanks
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Old   March 24, 2011, 21:40
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The sharp kink in the streamline is because you are using the variable "Velocity" for the streamlines, which is relative to the local frame of reference. At a change of frame of reference the velocity will not be continuous.

If you use "Velocity in stationary frame" all the velocities will be relative to the stationary frame and your streamlines will be smooth.
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Old   March 25, 2011, 13:20
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Thank you for your advice.
I will try that and will let you know how it goes.
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