Two boundary conditions in one patch

kraf · July 16, 2021, 01:51

Hello!

Newbie here.
I'm trying to simulate turbulent flow in a open channel. At the bottom of the channel, I want to define the following boundary conditions dU/dz=0 and U=0. Is there any boundary that can do that? It seems that I need to combine a zerogradient (dU/dz)+ fixedvalue (u=0). Does anybody has some idea?

Thank you in advance.

piu58 · July 16, 2021, 03:58

That does not work. These conditions contradict each other.

kraf · July 18, 2021, 20:05

Dear Uwe Pilz
Thank you for your reply.
I see. What about imposing one condition in one region and the other in the second region? I'm attaching a picture of what I would like to impose as boundary condition.
Thank you for your help in advance.

Kojote · July 19, 2021, 07:00

Hi, i do not know if this help but you can use swak4foam and teh use the groovyBCdirecton which is very powerfull. Maybe this fix your problem.

Br

Christian

July 16, 2021, 01:51	Two boundary conditions in one patch	#1
kraf New Member Ibaraki Join Date: Jul 2021 Posts: 9 Rep Power: 5	Hello! Newbie here. I'm trying to simulate turbulent flow in a open channel. At the bottom of the channel, I want to define the following boundary conditions dU/dz=0 and U=0. Is there any boundary that can do that? It seems that I need to combine a zerogradient (dU/dz)+ fixedvalue (u=0). Does anybody has some idea? Thank you in advance.

July 16, 2021, 03:58		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	That does not work. These conditions contradict each other. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

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July 19, 2021, 07:00		#4
Kojote Member Join Date: Aug 2011 Posts: 37 Rep Power: 15	Hi, i do not know if this help but you can use swak4foam and teh use the groovyBCdirecton which is very powerfull. Maybe this fix your problem. Br Christian