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August 7, 2012, 00:17 |
Torque Prediction
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#1 |
Member
DB
Join Date: Apr 2011
Posts: 87
Rep Power: 15 |
Dear All,
I am simulating a flow over a ceiling fan in an enclosed room. the fan is rotating at speeds in the range of 300-400 RPM. I am defining a rotating domain around the fan and following the frozen rotor approach. The fan blade is only 1 mm thick. I have tried to predict the torque over the fan, the error varies from 15-60% from the actual value for various cases. However the mass flow variation is well within 2% of experiments. I recently approached ANSYS support for it and they suggested going for y plus value for first cell as 1 as I am using SST model. But because of that the error increased further by 10% in torque and to 20% in mass flow ( y did this happen ? ) Can anyone suggest how to improve my accuracy and consistency of such a simulation.
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-D.B |
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August 7, 2012, 01:54 |
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#2 |
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Dynampally Pavitran
Join Date: Mar 2010
Location: India
Posts: 74
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August 7, 2012, 19:26 |
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#3 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
Have you read this FAQ? http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F
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August 8, 2012, 00:02 |
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#4 |
Member
DB
Join Date: Apr 2011
Posts: 87
Rep Power: 15 |
Hi Glenn,
Yes I have read that a number of times. Still I couldnt find a solution to my problem. One additional thing, by reducing yplus to below 1, my solution is not converging properly, my residuals are stable ( although high ) but my torque changes with every iteration it has already been around 1400 iterations. How should I get a stable and accurate solution for my problem.
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August 8, 2012, 00:12 |
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#5 | |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
Quote:
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August 8, 2012, 01:58 |
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#6 |
Member
DB
Join Date: Apr 2011
Posts: 87
Rep Power: 15 |
Hi ghorrocks,
My simulation is quite a low rpm and low blade loading simulation. It does not involve flow separation.
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August 8, 2012, 07:44 |
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#7 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
Then you should be able to get an accurate result for this model.
Can you post some images and your CCL? Maybe the output file too. |
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September 19, 2013, 05:35 |
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#8 | |
New Member
Triloka Tankala
Join Date: Sep 2013
Posts: 2
Rep Power: 0 |
Quote:
I also have the same issue in terms of torque prediction. The CFM predictions are quite good. But the torque predictions are varying from 0 to 50%. Did you get any breakthrough?We are trying several methods and didnt get any success. Please reply to my email id: trilok99@gmail.com |
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September 19, 2013, 05:55 |
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#9 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
What you need to do for an accurate simulation is described in the link I posted in post #3.
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