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-   -   Residual target for turbulence transport equations (http://www.cfd-online.com/Forums/cfx/109025-residual-target-turbulence-transport-equations.html)

saisanthoshm88 November 7, 2012 10:44

Residual target for turbulence transport equations
 
The CFX documentation states that the CFX solver internally uses a residual target of 10 times the specified value for the turbulence transport equations..

Could some one please explain the reason for this.

I know that residuals are not the only criteria to judge convergence and that one needs to look up for monitor points, flow imbalances and even see from the post processing if the obtained results make a complete physical sense.

Despite knowing all this I still have this question about the residuals.

My only interest is to know why such relatively large residual target is internally chosen for the turbulence transport equations by the CFX solver.

Could some one please provide an explanation.

ghorrocks November 7, 2012 17:40

The turbulence equations do not directly affect the flow. They only have a weak coupling by affecting the viscosity or diffusivity (for 2-eqn models anyway). So as the coupling is weak then convergence can be looser and accuracy will not suffer (for most applications anyway).

saisanthoshm88 November 8, 2012 02:03

Many thanks for the clarification glenn


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