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-   -   Turbulent cyclic pipe flow, wall functions and y+ (http://www.cfd-online.com/Forums/openfoam-solving/91892-turbulent-cyclic-pipe-flow-wall-functions-y.html)

clyde August 25, 2011 15:40

Turbulent cyclic pipe flow, wall functions and y+
 
Sorry for the newbie question but I am just learning this stuff.

I have modeled a cyclic pipe in 3D with a modified simpleFoam solver to include a pressure gradient in the Ueqn to drive the flow.

Question is; what is the appropriate value for y+ when using the kEpsilon model with wall functions? Re=38700 so its fully turbulent. My issue is that i would expect the desired y+ to be about ~10.6 corresponding to the intersection of the wall and log laws. After modifying my mesh to achieve this by placing the first node from the wall at y+=10.6 i dont get the desired effect when i plot u+ vs y+. Instead of a 'knee in the curve' at y+=10.6 its closer to y+=25.

clyde August 26, 2011 10:28

1 Attachment(s)
Attached is a graph of u+ vs y+ from my case.

medy77865 January 10, 2014 18:30

I am like you newbie.

I am also interested in your this post. Please let me know about your findings.

wzx1989221 March 17, 2014 07:08

Hi clyde,

I am also doing turbulent pipe flow in OF. May I ask you that how do you get the mean velocity profile (for my pipe flow I don't know how to do field average in streamwise and circumferential directions)? It would be great if you can give me a hint on that and I really appreciate it.

Thank you very much.

Kind regards,
Tony


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