Convergence

sampathevs · December 19, 2013, 01:50

Hi all,
(In FLUENT 14.5)

My solution is converged and all the flow rates etc got balanced. Even my plots are according to my expectations. But, the residuals got settled at e-02.

Any tips or tricks to make lower these residuals , at-least till e-04.

1. Tried by changing URF's. Need any other suggestions.
2. Done standard initialization ( Tried with hybrid as well, but obtained same result)

3. Trying for first order convergence

Will be glad if anyone can reply .

Thanks and Regards,
Sampath Emani

foamcfd · December 19, 2013, 12:00

If you are satisfied with the results then you shouldn't worry about the residual values. Residual is one of convergence criteria and not the convergence criteria. You can also monitor variables at various location to make sure that solution is converged.

If you have natural convection in your problem then you are more likely to get residual which you are getting. Try flipping URF for pressure and momentum if you are using seggregated solver.

sampathevs · December 20, 2013, 01:06

Hi,

Thanks for the reply.

I gave outflow boundary condition to the outlet. Hence, the residuals got stuck at e-02. When i tried by changing it to pressure outlet, residuals got reduced till 4.
this is for species transport simulation.

Regards,
Sampath emani.

December 19, 2013, 01:50	Convergence	#1
sampathevs Member EMAVI V SURYA SAMPATH Join Date: Aug 2011 Location: Malaysia Posts: 85 Rep Power: 15	Hi all, (In FLUENT 14.5) My solution is converged and all the flow rates etc got balanced. Even my plots are according to my expectations. But, the residuals got settled at e-02. Any tips or tricks to make lower these residuals , at-least till e-04. 1. Tried by changing URF's. Need any other suggestions. 2. Done standard initialization ( Tried with hybrid as well, but obtained same result) 3. Trying for first order convergence Will be glad if anyone can reply . Thanks and Regards, Sampath Emani

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December 19, 2013, 12:00		#2
foamcfd New Member Yogesh Patil Join Date: Nov 2009 Posts: 20 Rep Power: 17	If you are satisfied with the results then you shouldn't worry about the residual values. Residual is one of convergence criteria and not the convergence criteria. You can also monitor variables at various location to make sure that solution is converged. If you have natural convection in your problem then you are more likely to get residual which you are getting. Try flipping URF for pressure and momentum if you are using seggregated solver.

December 20, 2013, 01:06		#3
sampathevs Member EMAVI V SURYA SAMPATH Join Date: Aug 2011 Location: Malaysia Posts: 85 Rep Power: 15	Hi, Thanks for the reply. I gave outflow boundary condition to the outlet. Hence, the residuals got stuck at e-02. When i tried by changing it to pressure outlet, residuals got reduced till 4. this is for species transport simulation. Regards, Sampath emani.