# how to check the convergence situation in one time step

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 November 16, 2017, 04:57 how to check the convergence situation in one time step #1 New Member   linlin.geng Join Date: Oct 2017 Posts: 22 Rep Power: 8 when we do unsteady simulation, we can set different iteration number for one time step. if i set the interation number to 100, how can i know the convergence situation for this 100 interations in CFX-Slover.

 November 16, 2017, 05:07 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 For most simulations the residuals are the best measure of convergence. Some simulations require imbalances as well. Most people set up transient simulations to converge to a specified residual as the criteria for convergence in each time step.

November 16, 2017, 05:11
#3
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linlin.geng
Join Date: Oct 2017
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Quote:
 Originally Posted by ghorrocks For most simulations the residuals are the best measure of convergence. Some simulations require imbalances as well. Most people set up transient simulations to converge to a specified residual as the criteria for convergence in each time step.
I know what you mean, but i want to check the convergence of residuals in each time step with some interations. what should i do.

 November 16, 2017, 05:23 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 The solver manager shows you the residuals. For a transient simulation you can just show the residual of the last iteration in each time step or you can show the residual of all iterations.

November 16, 2017, 05:33
#5
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Peter
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Quote:
 Originally Posted by ghorrocks The solver manager shows you the residuals. For a transient simulation you can just show the residual of the last iteration in each time step or you can show the residual of all iterations.
To activate the residual convergence you have to activate the "Monitor Coefficient Loop Convergence" in the Output Control/Monitor Tab in Pre. Then you can switch between all/last residuals in the Solver Manager (Workspace Properties/Global Plot Settings/Plot Coefficient Loop Data)

November 16, 2017, 05:33
#6
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linlin.geng
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Quote:
 Originally Posted by ghorrocks The solver manager shows you the residuals. For a transient simulation you can just show the residual of the last iteration in each time step or you can show the residual of all iterations.
if I want to check the convergence situation of a specific moniter point, the solver manager can not show me the information about this.

November 16, 2017, 06:09
#7
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linlin.geng
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Quote:
 Originally Posted by PeMo To activate the residual convergence you have to activate the "Monitor Coefficient Loop Convergence" in the Output Control/Monitor Tab in Pre. Then you can switch between all/last residuals in the Solver Manager (Workspace Properties/Global Plot Settings/Plot Coefficient Loop Data)
I get your point, and I get what i want. thank you very much.

 November 16, 2017, 16:21 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 To get the convergence at a specific point, define a monitor point at that location and assign your convergence variable to it. That would probably be the residual for one of the equations but it could be something else. Then you can see the convergence at that point in Solver Manager as the simulation progresses. aero_head likes this.