boundary conditions

Pavel O · September 30, 2009, 16:30

I have a problem with bc 'pressure outlet'. When the flow reaches the edge of domain with this bc the process is not converged. What should be set for this bc?. Could you please helop me with this.

Many thanks

timjm · October 1, 2009, 13:10

I used to have that problem too.

You can either re-mesh at that outlet so it is more refined, or try and relax your tolerances.

I would try the tolerances first and then let it come to a converged solution.

Also, sometimes it just takes a while for the pressure outlet to have convergence at all the nodes.

Pavel O · October 1, 2009, 13:32

Many thanks,
I will try to do both. As I understood the mesh should be more fine on the pressure outlet? In my case it is slightly coarser.

owais70 · October 1, 2009, 16:30

Check if you have reverse flow at the outlet. Add a length/domain at the outlet.

Pavel O · October 2, 2009, 08:49

I set momentum boundary condition 'pressure gauge' to -10, and I had no back flow. I tried to extend domain but only effect I got it was extend of time of converged process. In some cases it helps and after some time process is converged again, but not every time.

Many thanks

September 30, 2009, 16:30	boundary conditions	#1
Pavel O New Member Join Date: Sep 2009 Posts: 4 Rep Power: 16	I have a problem with bc 'pressure outlet'. When the flow reaches the edge of domain with this bc the process is not converged. What should be set for this bc?. Could you please helop me with this. Many thanks

October 1, 2009, 16:30	pressure bc	#4
owais70 New Member mangal Join Date: Oct 2009 Location: Canada Posts: 7 Rep Power: 16	Check if you have reverse flow at the outlet. Add a length/domain at the outlet.

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October 1, 2009, 13:10		#2
timjm New Member Tim Maguire Join Date: Sep 2009 Posts: 19 Rep Power: 16	I used to have that problem too. You can either re-mesh at that outlet so it is more refined, or try and relax your tolerances. I would try the tolerances first and then let it come to a converged solution. Also, sometimes it just takes a while for the pressure outlet to have convergence at all the nodes.

October 1, 2009, 13:32		#3
Pavel O New Member Join Date: Sep 2009 Posts: 4 Rep Power: 16	Many thanks, I will try to do both. As I understood the mesh should be more fine on the pressure outlet? In my case it is slightly coarser.

October 2, 2009, 08:49		#5
Pavel O New Member Join Date: Sep 2009 Posts: 4 Rep Power: 16	I set momentum boundary condition 'pressure gauge' to -10, and I had no back flow. I tried to extend domain but only effect I got it was extend of time of converged process. In some cases it helps and after some time process is converged again, but not every time. Many thanks