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-   -   2D flow around a rotating cylinder (http://www.cfd-online.com/Forums/fluent/71269-2d-flow-around-rotating-cylinder.html)

king lui December 22, 2009 16:26

2D flow around a rotating cylinder
 
Hey everybody,:confused::confused::confused:

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

anshulmittal1912 December 22, 2009 21:59

How are you treating the walls? Are you using the standard wall functions?

king lui December 23, 2009 11:59

Quote:

Originally Posted by anshulmittal1912 (Post 240778)
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.

anshulmittal1912 December 23, 2009 20:53

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

king lui December 24, 2009 06:46

Quote:

Originally Posted by anshulmittal1912 (Post 240853)
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

king lui December 24, 2009 07:56

just one question, where i can find the fluent manual for the version 6.3.26
cause the links in the forum donīt work:o


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