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transient analysis from steady data

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Old   May 21, 2013, 08:10
Exclamation transient analysis from steady data
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Francesco
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Hi everybody,
I usually perform steady simulations by CFX without troubles.
Now I need to perform a transient analysis in order to understand the flow field insiede a pump.
I would like to know I can I perform a transient simulation from data of a finished steady run.

Thanks in advance.
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Old   May 21, 2013, 08:51
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OJ
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Just initialize the transient run using the steady res files in Define Run dialogue box.

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Old   May 21, 2013, 19:23
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And use adaptive time stepping, homing in on 3-5 coeff loops per iteration to set the time step. Probably the most common problem in transient simulation on this forum is people who set a time step size which is way off.
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Old   May 22, 2013, 03:41
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Francesco
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Thanks guys.

Could you please help me to fill out the basic settings tab as you can see in the file attached.
I want to get an animation of my impeller motion and flow field around. Its speed is 8750 rpm. I want to simulate in 10 frames a total time of 0.000403 seconds.

Thank you!
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File Type: jpg settings.jpg (46.5 KB, 8 views)
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Old   May 22, 2013, 05:52
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Initial timestep=1e-8[s]
max TS=1e20
min TS=1e-20

That will do. The initial TS is almost certainly too small, but it will quickly find the correct size. Next time you run it you can put the correct initial TS in and you will save some time.

For the animation make sure you save transient results files at time intervals suitable for what you want to see.
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Old   May 22, 2013, 08:00
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Thank you so much! I gonna try!
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