Regarding problem with the buoyantBoussinesqPimpleFoam solver.

tintintk · March 21, 2018, 09:38

Hello everyone.

I am trying to simulate flow in a nozzle using the buoyantBoussinesqPimpleFoam solver. But at the outflow i am getting back-flow. I have tried all the possible boundary condition.
I am also attaching the case file for the reference and the screenshot the problem that i am getting.

the screen shot attached shows the problem at the outlet..where instead of getting the fully developed profile i am getting two recirculating zones.

Thank you in advance.

clapointe · March 22, 2018, 22:41

Try an inletOutlet condition for your velocity at the outlet.

Caelan

piu58 · March 23, 2018, 01:57

If you use an outflow b.c. you should have an outflow stream there: The flow should not contain any backflow components. The flow property you set (zeroGradient) should be realized by the flow itself.

I recommend to simulate a longer region for stabilizing the flow. Usual, 10 times the size of obstacles is the required minimum. You don't have an obstacle, so I recommend 10 times the size of the large eddies.

tintintk · March 26, 2018, 02:20

Quote:

Originally Posted by piu58

If you use an outflow b.c. you should have an outflow stream there: The flow should not contain any backflow components. The flow property you set (zeroGradient) should be realized by the flow itself.

I recommend to simulate a longer region for stabilizing the flow. Usual, 10 times the size of obstacles is the required minimum. You don't have an obstacle, so I recommend 10 times the size of the large eddies.

Thank you for the suggestions. I will try to implement it.

tintintk · March 26, 2018, 02:20

Quote:

Originally Posted by clapointe

Try an inletOutlet condition for your velocity at the outlet.

Caelan

I have also tried this boundary condition but of no use.

March 23, 2018, 01:57		#3
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	If you use an outflow b.c. you should have an outflow stream there: The flow should not contain any backflow components. The flow property you set (zeroGradient) should be realized by the flow itself. I recommend to simulate a longer region for stabilizing the flow. Usual, 10 times the size of obstacles is the required minimum. You don't have an obstacle, so I recommend 10 times the size of the large eddies. __________________ 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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March 22, 2018, 22:41		#2
clapointe Senior Member Join Date: Aug 2015 Posts: 494 Rep Power: 15	Try an inletOutlet condition for your velocity at the outlet. Caelan