Problem with convergence of continuity

Clémence · August 12, 2014, 04:03

Why do you think continuity doesn't converge on my simulation? And how could I make it converge without changing the mesh?

For information: I have a geometry of 14 m and aroud 1 million cells. Cells has a base size of 5 cm, which I know is high. I am running in implicit unsteady with time step of 0.01s and a CFL between 1 and 10.

Thank you!

Mricart · August 19, 2014, 11:37

Have you checked if the force converge / stabilize? I have read in some places that the residuals in Star-CCM+ are not that important. Besides, all the other goes down quiet a lot.

Mricart · August 19, 2014, 11:38

You can always check what happens if you change the turbulence models

Clémence · August 20, 2014, 11:55

Thank you for your answer Mricart.

Actually I already found why continuity was not converging. I was using coupled solver but it was not adapted to my case. With the segregated olver, the convergence is much better.

But there is still some convergence issue. For exemple, in the middle of the time step, residuals make a pic and there is this error message:
Bi-conjugate gradient stabilized solver did not converge !

August 20, 2014, 11:55		#4
Clémence New Member Join Date: May 2014 Posts: 12 Rep Power: 12	Thank you for your answer Mricart. Actually I already found why continuity was not converging. I was using coupled solver but it was not adapted to my case. With the segregated olver, the convergence is much better. But there is still some convergence issue. For exemple, in the middle of the time step, residuals make a pic and there is this error message: Bi-conjugate gradient stabilized solver did not converge ! rgd likes this.

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August 19, 2014, 11:37		#2
Mricart New Member Marc Ricart Rius Join Date: May 2014 Posts: 7 Rep Power: 12	Have you checked if the force converge / stabilize? I have read in some places that the residuals in Star-CCM+ are not that important. Besides, all the other goes down quiet a lot.

August 19, 2014, 11:38		#3
Mricart New Member Marc Ricart Rius Join Date: May 2014 Posts: 7 Rep Power: 12	You can always check what happens if you change the turbulence models