Virtual volumes

Mohsin · March 23, 2010, 11:03

Hello

I made a cylinder shape in gambit and i have to insert pulverized coal from upside. I divided the inlet of the cylinder into 4 sections by real connected edges (because i wanted to have flow in just 2 sections for showing non uniformity in flow). But Fluent is giving residual of 10^-2 for turbulent Epsilon and dissipation and other quantities not less than 10^-3 Which shows that the result is not converged.

I am unable to guess what is the problem. i reduced the turbulent intenisties for boundary conditions also but same result. May be its a geomerty problem or may be I used real edges at the inlet of the cylinder.

My main question is that if i make virtual edges for inlet section then what is the benefit of it. Why peopel go for virtual volumes and virtual faces what is the benefit of working in Virtual field. I know you cant apply Bolean operations etc on virtual volume but can anybody tell me the benefit Please? and also why my result was diverging.

I will be so thankful for your help.
MOHSIN

-mAx- · March 24, 2010, 02:01

If I had the choice I would stay and work with real entities. But sometime, due to complexity to your geometry, gambit converts some entity into virtual.
But it has no influence on convergence etc..

Mohsin · March 24, 2010, 03:32

Thank you for your answer Max.

I would appreciate if you answer to this thread as well

http://www.cfd-online.com/Forums/flu...-controls.html

Thank you.

March 23, 2010, 11:03	Virtual volumes	#1
Mohsin Senior Member Mohsin Mukhtar Join Date: Mar 2010 Location: South Korea Posts: 249 Rep Power: 17	Hello I made a cylinder shape in gambit and i have to insert pulverized coal from upside. I divided the inlet of the cylinder into 4 sections by real connected edges (because i wanted to have flow in just 2 sections for showing non uniformity in flow). But Fluent is giving residual of 10^-2 for turbulent Epsilon and dissipation and other quantities not less than 10^-3 Which shows that the result is not converged. I am unable to guess what is the problem. i reduced the turbulent intenisties for boundary conditions also but same result. May be its a geomerty problem or may be I used real edges at the inlet of the cylinder. My main question is that if i make virtual edges for inlet section then what is the benefit of it. Why peopel go for virtual volumes and virtual faces what is the benefit of working in Virtual field. I know you cant apply Bolean operations etc on virtual volume but can anybody tell me the benefit Please? and also why my result was diverging. I will be so thankful for your help. MOHSIN

March 24, 2010, 02:01		#2
-mAx- Super Moderator Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41	If I had the choice I would stay and work with real entities. But sometime, due to complexity to your geometry, gambit converts some entity into virtual. But it has no influence on convergence etc.. __________________ In memory of my friend Hervé: CFD engineer & freerider

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March 24, 2010, 03:32		#3
Mohsin Senior Member Mohsin Mukhtar Join Date: Mar 2010 Location: South Korea Posts: 249 Rep Power: 17	Thank you for your answer Max. I would appreciate if you answer to this thread as well http://www.cfd-online.com/Forums/flu...-controls.html Thank you.