How to check the convergence of the CFX solver?

Amoul · May 24, 2013, 04:30

Hello,
I would like to know how i can make sure that my solver is definitely converging. In other words, what should i check in the out. file ? (how should the residual values be?)
Knowing that i am using:
-steady state solution
-CFX stand alone mode
-High resolution scheme
PS: The FAQ of CFD online did not help me at all!
Thank you,

ghorrocks · May 24, 2013, 06:13

There is a section in the CFX documentation on obtaining convergence.

Amoul · May 24, 2013, 06:24

What is your own method?

ghorrocks · May 24, 2013, 06:26

Residuals always, imbalances sometimes, other important parameters (lift, drag, pressure loss) sometimes.

Amoul · May 24, 2013, 06:31

would you please explain in details what you check exactly in the residuals?

ghorrocks · May 24, 2013, 06:40

Have you read the section on obtaining convergence? I hope you are not expecting me to re-type the entire chapter of the documentation.

Amoul · May 24, 2013, 06:48

Of course not!
Ok! and thank you very much for your help

siw · May 24, 2013, 06:57

Another useful resource:

http://www.computationalfluiddynamic...pendent-study/

In fact, it is worth reading all of the LEAP Australia blogs as there is lots of useful information - which would save lots of people having to make forum topics.

Amoul · May 24, 2013, 07:00

Thanks a lot Stuart

Inconel · May 30, 2013, 05:46

Hi, im new to OpenFoam.

I simulated a cyclon. The results in paraview are looking good, compered to other cylon simulations with cfd.

Now I want to do a Convergence Study with the pressure drop, but I dont know how i can implement to OpenFoam to calculate the pressure drop. In the tutorial that i use, there is a folder created "forces" in witch there is a text data "forceCoeffs.dat". There is the cd-Value saved. I can export these data to excel and do the Convergence Study with the cd-Value, but i want to do it with the Pressure drop. But the Pressure drop is not calulated. Can someone explain how to do it. I read through "computationalfluiddynamics.com.au/convergence-and-mesh-independent-study/" but it is mentioned that you can do it with the pressure drop, but it is not discribed how.

ghorrocks · May 30, 2013, 05:57

This is the CFX forum, try the openfoam forum.

May 24, 2013, 04:30	How to check the convergence of the CFX solver?	#1
Amoul New Member Candy Join Date: May 2013 Posts: 12 Rep Power: 12	Hello, I would like to know how i can make sure that my solver is definitely converging. In other words, what should i check in the out. file ? (how should the residual values be?) Knowing that i am using: -steady state solution -CFX stand alone mode -High resolution scheme PS: The FAQ of CFD online did not help me at all! Thank you,

May 24, 2013, 06:40		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Have you read the section on obtaining convergence? I hope you are not expecting me to re-type the entire chapter of the documentation. MUMMED likes this.

May 24, 2013, 06:57		#8
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 733 Rep Power: 25	Another useful resource: http://www.computationalfluiddynamic...pendent-study/ In fact, it is worth reading all of the LEAP Australia blogs as there is lots of useful information - which would save lots of people having to make forum topics. Amoul likes this.

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May 24, 2013, 06:13		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	There is a section in the CFX documentation on obtaining convergence.

May 24, 2013, 06:24		#3
Amoul New Member Candy Join Date: May 2013 Posts: 12 Rep Power: 12	What is your own method?

May 24, 2013, 06:26		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Residuals always, imbalances sometimes, other important parameters (lift, drag, pressure loss) sometimes.

May 24, 2013, 06:31		#5
Amoul New Member Candy Join Date: May 2013 Posts: 12 Rep Power: 12	would you please explain in details what you check exactly in the residuals?

May 24, 2013, 06:48		#7
Amoul New Member Candy Join Date: May 2013 Posts: 12 Rep Power: 12	Of course not! Ok! and thank you very much for your help

May 24, 2013, 07:00		#9
Amoul New Member Candy Join Date: May 2013 Posts: 12 Rep Power: 12	Thanks a lot Stuart

May 30, 2013, 05:46		#10
Inconel New Member David Join Date: May 2013 Posts: 2 Rep Power: 0	Hi, im new to OpenFoam. I simulated a cyclon. The results in paraview are looking good, compered to other cylon simulations with cfd. Now I want to do a Convergence Study with the pressure drop, but I dont know how i can implement to OpenFoam to calculate the pressure drop. In the tutorial that i use, there is a folder created "forces" in witch there is a text data "forceCoeffs.dat". There is the cd-Value saved. I can export these data to excel and do the Convergence Study with the cd-Value, but i want to do it with the Pressure drop. But the Pressure drop is not calulated. Can someone explain how to do it. I read through "computationalfluiddynamics.com.au/convergence-and-mesh-independent-study/" but it is mentioned that you can do it with the pressure drop, but it is not discribed how.

May 30, 2013, 05:57		#11
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	This is the CFX forum, try the openfoam forum.