Residuals Plot

kamalipour · December 13, 2011, 08:30

Hello everyone.
as I am new to this good site, I have a lot of questions about Fluent and GAMBIT. Hope you help me.
I start my first question about Residuals Plot.
What mean Residuals Plot?
How it should be?
Thank you dears.

kvloover · December 14, 2011, 16:45

In theory the residual is the difference between your current (iterated) value and the exact solution.
Now since fluent doesn't know the exact solution, afaik the residual is the difference between the values of two iterations. (be it maximum, weighted or...)

A small residual in principal gives the more accurate solution. However the mesh can converge to a wrong value if it's not made properly. For this a seperate mesh/grid independance study is needed.

A decent value for the momentum residual would be E-05.
(And it should overall be going down -even slowly-, else it's unstable)

kamalipour · December 15, 2011, 04:44

Thank you dear Kevin for your reply.
How to understand that converge is wrong? Is this possible?
and can you suggest me a refrance for studding about mesh/grid?

December 13, 2011, 08:30	Residuals Plot	#1
kamalipour New Member Abdollah Kamalipour Join Date: Dec 2011 Location: Isfahan Posts: 2 Rep Power: 0	Hello everyone. as I am new to this good site, I have a lot of questions about Fluent and GAMBIT. Hope you help me. I start my first question about Residuals Plot. What mean Residuals Plot? How it should be? Thank you dears.

December 14, 2011, 16:45		#2
kvloover New Member Kevin Van Looveren Join Date: Nov 2011 Posts: 11 Rep Power: 15	In theory the residual is the difference between your current (iterated) value and the exact solution. Now since fluent doesn't know the exact solution, afaik the residual is the difference between the values of two iterations. (be it maximum, weighted or...) A small residual in principal gives the more accurate solution. However the mesh can converge to a wrong value if it's not made properly. For this a seperate mesh/grid independance study is needed. A decent value for the momentum residual would be E-05. (And it should overall be going down -even slowly-, else it's unstable) kamalipour likes this.

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December 15, 2011, 04:44		#3
kamalipour New Member Abdollah Kamalipour Join Date: Dec 2011 Location: Isfahan Posts: 2 Rep Power: 0	Thank you dear Kevin for your reply. How to understand that converge is wrong? Is this possible? and can you suggest me a refrance for studding about mesh/grid?