Symmetry model half or total geometrical model in LES

vvqf · March 21, 2006, 10:34

hi dear all,

if the model is symmetric, can we use just half geometrical model in LES ?
as i remember in the tutorial, it is ok for turbFoam, but i am not sure in OpenFoam if it's also ok for LES.

Thanks

pierre · March 21, 2006, 13:52

Do you mean the geometry of the domain is symmetric? In which case your computational domain can be reduced as long as the 3D eddy structures of turbulence resolved by the LES model can be captured correclty, it's very case dependent. I.e. in pipes, bad idea. In a backward step case, the width should be as large as necessary, and so on.

Pierre

vvqf · March 22, 2006, 07:31

Hi Pierre,
Thanks for the answer.

and I just read,
Geometry for LES
"Even though there might be symmetries in the geometry and flow, the geometrical model should include the full region, since, while the time averaged flows may be symmetric, the instantaneous flows are not, and restricting the domain could constrain the turbulence. Two-dimensional approximations are particularly poor. "

It talks about the general case in CFX, I think in OpenFoam it might be simlilar.

vivekcfd · March 22, 2006, 09:06

Never think of simplifying a geometry when you are using LES. What ever code it is, LES has to be with full realistic geometry. There is no chance that the instantaneous fields are symmetric in a full turbulent case.
VK

March 21, 2006, 10:34	hi dear all, if the model i	#1
vvqf Member VVqf Join Date: Mar 2009 Location: Braunschweig Posts: 66 Rep Power: 17	hi dear all, if the model is symmetric, can we use just half geometrical model in LES ? as i remember in the tutorial, it is ok for turbFoam, but i am not sure in OpenFoam if it's also ok for LES. Thanks

March 21, 2006, 13:52	Do you mean the geometry of th	#2
pierre Member Pierre Le Fur Join Date: Mar 2009 Location: UK Posts: 60 Rep Power: 17	Do you mean the geometry of the domain is symmetric? In which case your computational domain can be reduced as long as the 3D eddy structures of turbulence resolved by the LES model can be captured correclty, it's very case dependent. I.e. in pipes, bad idea. In a backward step case, the width should be as large as necessary, and so on. Pierre

March 22, 2006, 07:31	Hi Pierre, Thanks for the an	#3
vvqf Member VVqf Join Date: Mar 2009 Location: Braunschweig Posts: 66 Rep Power: 17	Hi Pierre, Thanks for the answer. and I just read, Geometry for LES "Even though there might be symmetries in the geometry and flow, the geometrical model should include the full region, since, while the time averaged flows may be symmetric, the instantaneous flows are not, and restricting the domain could constrain the turbulence. Two-dimensional approximations are particularly poor. " It talks about the general case in CFX, I think in OpenFoam it might be simlilar.

March 22, 2006, 09:06	Never think of simplifying a g	#4
vivekcfd Member Vivek Kumar Join Date: Mar 2009 Location: Switzerland Posts: 35 Blog Entries: 1 Rep Power: 17	Never think of simplifying a geometry when you are using LES. What ever code it is, LES has to be with full realistic geometry. There is no chance that the instantaneous fields are symmetric in a full turbulent case. VK lvl99 likes this.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Half laminar and turbulent model trying to solve	Andrew Clarke	FLUENT	5	May 19, 2008 13:40
Kinetic air props model - conductivity HALF?	Chris Bailey	FLUENT	1	March 7, 2006 10:38
3d half model airplane simulation	Loh	FLUENT	2	January 17, 2006 22:36
Can We Model Spherical Symmetry in CFX	ashishraval	CFX	2	May 1, 2004 14:14
3d and half model	nikita	FLUENT	0	April 22, 2003 03:41