Velocity outflow boundary condition

rexk · March 9, 2017, 02:38

Hi all,

If I am using code_saturne to model a convection problem and wish to define a velocity at outlet. Can I actually have velocity outflow type of boundary condition? As I see most of the time CFD users use pressure outflow type ?

Thanks!

lcarasik · March 9, 2017, 15:54

Quote:

Originally Posted by rexk

Hi all,

If I am using code_saturne to model a natural convection problem and wish to define a velocity at outlet. Can I actually have velocity outflow type of boundary condition? As I see most of the time CFD users use pressure outflow type ?

Thanks!

Why are you trying to define a velocity at the outlet if it is natural convection?

piu58 · March 10, 2017, 00:14

For a free outflow a zero gradient velocity is appropriate.

rexk · March 10, 2017, 00:34

Quote:

Originally Posted by lcarasik

Why are you trying to define a velocity at the outlet if it is natural convection?

Forgive me, I wish to define a velocity to make it forced convection....

lcarasik · March 14, 2017, 01:34

Quote:

Originally Posted by rexk

Forgive me, I wish to define a velocity to make it forced convection....

Ah sorry, I read it originally as natural convection. A good combination is a velocity inlet and a pressure outlet.

rexk · March 23, 2017, 23:05

Quote:

Originally Posted by lcarasik

Ah sorry, I read it originally as natural convection. A good combination is a velocity inlet and a pressure outlet.

Do you mean the velocity inlet and a pressure outlet in OpenFOAM? What if I am using the Code_Saturne ?

As for pressure outlet, meaning I have to convert the velocity into pressure then?

Thanks for patience in answering beginner's question

lcarasik · March 24, 2017, 01:04

Quote:

Originally Posted by rexk

Do you mean the velocity inlet and a pressure outlet in OpenFOAM? What if I am using the Code_Saturne ?

As for pressure outlet, meaning I have to convert the velocity into pressure then?

Thanks for patience in answering beginner's question

No, a velocity inlet and pressure outlet (zero gradient of all solver quantities) is a standard boundary condition pairing for any CFD analysis (involving convection) using ANY CFD code package.

I recommend taking a look at this powerpoint that discusses CFD boundary conditions, http://www.bakker.org/dartmouth06/engs150/06-bound.pdf.

March 9, 2017, 02:38	Velocity outflow boundary condition	#1
rexk New Member Rex Ken Join Date: Mar 2017 Posts: 5 Rep Power: 9	Hi all, If I am using code_saturne to model a convection problem and wish to define a velocity at outlet. Can I actually have velocity outflow type of boundary condition? As I see most of the time CFD users use pressure outflow type ? Thanks! Last edited by rexk; March 10, 2017 at 01:41.

March 10, 2017, 00:14		#3
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	For a free outflow a zero gradient velocity is appropriate. __________________ 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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