# 2D flow around a rotating cylinder

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 December 22, 2009, 16:26 2D flow around a rotating cylinder #1 New Member   Join Date: Dec 2009 Posts: 26 Rep Power: 9 Hey everybody, I have a problem by working with Fluent. The tolerance of my y+ value is between 50 and 500 but the range of the rotational speed of my cylinder is very large Therefore some problems occur for example if the cylinder is rotating by 100rpm the y+ value is in tolerance but if the cylinder is rotating with 1000rpm with the same settings the y+ is not anymore in the tolerance and therefore i use the function - adapt -yplus/ystar - adapt this pushes my y+ value back into its tolerance. i think this affects my accuracy when i do this adapt funtion because if i do this for example until 8000rpm and always push my y+ into its tolerance and go back at the end from 8000rpm to a smaller value for example 500rpm the adapt function is necessary again and after that my result of the lift has a big deviation from my first result in the case of 500rpm. maybe someone can help me with that problem, thanks a lot for that

 December 22, 2009, 21:59 #2 New Member   Anshul Mittal Join Date: Apr 2009 Posts: 8 Rep Power: 10 How are you treating the walls? Are you using the standard wall functions?

December 23, 2009, 11:59
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 Originally Posted by anshulmittal1912 How are you treating the walls? Are you using the standard wall functions?
yes, i am using the viscous model k-epsilon with its standard settings, so with standard wall functions.

 December 23, 2009, 20:53 #4 New Member   Anshul Mittal Join Date: Apr 2009 Posts: 8 Rep Power: 10 Take a look at the Fluent manual. It says that the wall functions are not good in regions where there is boundary layer separation. This might be the problem. I am not sure about the adapt function. Anshul

December 24, 2009, 06:46
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 Originally Posted by anshulmittal1912 Take a look at the Fluent manual. It says that the wall functions are not good in regions where there is boundary layer separation. This might be the problem. I am not sure about the adapt function. Anshul
okay, thats a useful information, i will try some things in fluent,
thanks for your help so far

 December 24, 2009, 07:56 #6 New Member   Join Date: Dec 2009 Posts: 26 Rep Power: 9 just one question, where i can find the fluent manual for the version 6.3.26 cause the links in the forum donīt work

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