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Strange high velocity in centrifugal pump simulation |
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July 15, 2014, 03:39 |
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#21 | |
Senior Member
Huang Xianbei
Join Date: Sep 2013
Location: Yangzhou,China
Posts: 302
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Quote:
Thank you for your reply, I think this is quite unusual, the yPlus should not vary so much between RANS and LES. I'll go on digging the reason Xianbei |
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August 12, 2014, 12:37 |
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#22 |
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Ye Zhang
Join Date: Dec 2009
Location: Delft,Netherland
Posts: 92
Rep Power: 16 |
Hi Xianbei,
I am wondering how do you set your initial condition for SRFSimpleFoam. Since I always get the computation divergent after a few steps. That the continuity errors become quite large. Do you have any idea how to overcome this problem? Thanks a lot! Best regards Ye |
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August 12, 2014, 20:35 |
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#23 | |
Senior Member
Huang Xianbei
Join Date: Sep 2013
Location: Yangzhou,China
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Rep Power: 13 |
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All the conditions are in the former replies. You should use 10-20 steps in one PIMPLE loop, which is nOuterCorrectors Hope it helps Xianbei |
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August 14, 2014, 03:20 |
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#24 |
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Ye Zhang
Join Date: Dec 2009
Location: Delft,Netherland
Posts: 92
Rep Power: 16 |
Hi Xianbei,
Thank you so much for your quick reply. I see your conditions setting. I will try my case further. I still have some questions: 1. Did you use only one channel or full impeller for your successful simulation? 2. Is you simulation RANS or LES? How can the mesh is so less? only 0.3 million? 3. Have you ever tried MRFSimpleFoam? Do you think only one channel or full impeller works by using MRFSimpleFoam solver? Thank a lot again. Best regards Ye |
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August 15, 2014, 01:39 |
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#25 | |
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Huang Xianbei
Join Date: Sep 2013
Location: Yangzhou,China
Posts: 302
Rep Power: 13 |
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2/ LES, structured mesh is used 3/ MRFSimpleFoam, this can be used in both one channel and full impeller |
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August 15, 2014, 02:14 |
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#26 |
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Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,297
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Hi Xianbei, from the fact y+ < 2.5 you can not conclude that the mesh is capable of being used for LES. LES also has strong requirements on the boundary mesh in z+ and x+ directions. That is the main reason why LES is computationally so expensive.
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August 15, 2014, 02:27 |
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#27 | |
Senior Member
Huang Xianbei
Join Date: Sep 2013
Location: Yangzhou,China
Posts: 302
Rep Power: 13 |
Quote:
Thank you for your reminding. In fact, the mesh now is further improved to be capable for LES. The mesh in the two directions is refined with totally 1 million grids. However, the result is not good comparing with the result obtained in Fluent with the same mesh. ,especially near the pressure side. I changed the pisoFoam by add Coriolis force and centrifugal force instead of using MRFSimpleFoam to speed up the calculation. I think it's the near wall treatment that cause the deviation. However, the only wallfuntion( used on hub and shroud whose y+>30) is nuSgsSpaldingWallFunction , no further near wall models can be chosen Xianbei |
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