Turbulent cyclic pipe flow, wall functions and y+

clyde · August 25, 2011, 15:40

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

Attached is a graph of u+ vs y+ from my case.

medy77865 · January 10, 2014, 17:30

I am like you newbie.

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

wzx1989221 · March 17, 2014, 06:08

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

August 25, 2011, 15:40	Turbulent cyclic pipe flow, wall functions and y+	#1
clyde New Member clyde douros Join Date: Aug 2011 Location: NJ Posts: 2 Rep Power: 0	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.

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January 10, 2014, 17:30		#3
medy77865 New Member Mehdi Join Date: Feb 2013 Posts: 1 Rep Power: 0	I am like you newbie. I am also interested in your this post. Please let me know about your findings.

March 17, 2014, 06:08		#4
wzx1989221 Member Tony Join Date: Nov 2013 Posts: 35 Rep Power: 12	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