can you share cylinder forces results ?

marine · March 29, 2010, 09:41

hello!

I'm trying to learn how calculate forces with OpenFOAM 1.6 and I'm doing simulation for a 2D cylinder of 1m diameter in an incompressible viscous flow with a velocity inlet of 1m/s (Re=1.10^6). I'm using simpleFoam and k-epsilon turbulence model. I'd like to know if someone already runned this simulation with thoses values (or even other) and would like to share the results for the forces on the cylinder.

Thanks a lot in advance.

Marine

bjr · March 29, 2010, 16:20

I've done similar, but with k-omega SST and on a geometry I can't provide you, but I did match drag results within 15%. I'd be happy to discuss, provide setup, discuss getting forces, etc.

i3enhamin@gmail.com

lin · March 29, 2010, 23:42

I remember that k-epsilon is not good for such simulation.

maruthamuthu_venkatraman · March 30, 2010, 05:20

Hello,
The results are based on Std-Wallfunctions with High-Re Models for smooth cylinder. I havent tested nutSpallartAllamarsWall function.

The experimental values are also varying very much. I recommend you to have a look at this paper for more Refernece about the experimental data.

http://ctr.stanford.edu/ResBriefs01/wang.pdf

Have a look at the Plots and Tables as attached.

Good luck !

marine · March 30, 2010, 11:40

Thanks for your answers and for the paper !

Lin which model do you think is better for such simulation?

lin · March 30, 2010, 23:27

Just try some other two-equation turbulence closure other than standard k-epsilon. I think those would be better.

marine · March 31, 2010, 13:03

Hi!

I tried differents simulations and I have very stranges results, they are so differents and the convergence of the calcul vary a lot between the simulations.
My BCs and results are in cylinder2d.zip, if you are interested in it and can't open the file I can send you by mail.
so I'd like to know if anyone knows why the results are so differents, and if I can improve my boundary conditions or my turbulent model?

thanks a lot !

Marine
[IMG]file:///C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/moz-screenshot-1.png[/IMG][IMG]file:///C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]

maruthamuthu_venkatraman · April 16, 2010, 05:45

Hello,
I hope you fixed the errors. If not just check these variables.

1. Type yPlusRAS and see the values and plot them in paraView. May be you are using wall function with inappropiate near wall spacing. Check it out.

2.check the discretization schemes as well. I guess you are use 1 st orders scheme for U.

3 Regarding BC's just review turbulence modelling for wilcox. Hope its clarifying you..

Good luck

March 29, 2010, 09:41	can you share cylinder forces results ?	#1
marine Member Marine Join Date: Mar 2010 Posts: 38 Rep Power: 16	hello! I'm trying to learn how calculate forces with OpenFOAM 1.6 and I'm doing simulation for a 2D cylinder of 1m diameter in an incompressible viscous flow with a velocity inlet of 1m/s (Re=1.10^6). I'm using simpleFoam and k-epsilon turbulence model. I'd like to know if someone already runned this simulation with thoses values (or even other) and would like to share the results for the forces on the cylinder. Thanks a lot in advance. Marine

March 29, 2010, 16:20	Kind of	#2
bjr Member Ben Racine Join Date: Mar 2009 Location: Seattle, WA, USA Posts: 62 Rep Power: 17	I've done similar, but with k-omega SST and on a geometry I can't provide you, but I did match drag results within 15%. I'd be happy to discuss, provide setup, discuss getting forces, etc. i3enhamin@gmail.com

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March 29, 2010, 23:42		#3
lin Senior Member Hua Zen Join Date: Mar 2009 Posts: 138 Rep Power: 17	I remember that k-epsilon is not good for such simulation.

March 30, 2010, 11:40		#5
marine Member Marine Join Date: Mar 2010 Posts: 38 Rep Power: 16	Thanks for your answers and for the paper ! Lin which model do you think is better for such simulation?

March 30, 2010, 23:27		#6
lin Senior Member Hua Zen Join Date: Mar 2009 Posts: 138 Rep Power: 17	Just try some other two-equation turbulence closure other than standard k-epsilon. I think those would be better.

April 16, 2010, 05:45		#8
maruthamuthu_venkatraman Member Maruthamuthu Venkatraman Join Date: Mar 2009 Location: Norway Posts: 80 Rep Power: 17	Hello, I hope you fixed the errors. If not just check these variables. 1. Type yPlusRAS and see the values and plot them in paraView. May be you are using wall function with inappropiate near wall spacing. Check it out. 2.check the discretization schemes as well. I guess you are use 1 st orders scheme for U. 3 Regarding BC's just review turbulence modelling for wilcox. Hope its clarifying you.. Good luck