Modeling of conditioned flow of interfaces

Pled · April 3, 2019, 09:57

Hello everyone.

Here is another question.
My problem is that I have liquid flow in two domains that have a common interface.
The interface allows a mass flow to one direction which is analogous to the wall shear stresses that are applied to it.
How can I model it in CFX, since I cannot write any conditional flow.

ghorrocks · April 3, 2019, 20:13

Have you looked at the options available to interfaces? You can specify a mass flow rate at interfaces, and you could make that a function of wall shear stresses or other variables.

Pled · April 4, 2019, 04:41

Yes, but this applies an equal distributed mass flow to the interface, not an variable one.

ghorrocks · April 4, 2019, 06:24

Then maybe make it a standard conservative connection, but use a momentum source term to control the flow locally as a function of anything you like.

Pled · April 4, 2019, 06:42

This would have been a good solution,
if cfx had enabled an option of momentum source in interfaces.
Unfortunately, cfx fails to my expectations again.
What do you thing of the idea of creating a thin subdomain,
instead of just a surface, and apply in it momentum sources?

ghorrocks · April 4, 2019, 06:59

The thin subdomain can work.

I can't check now, but I thought you could put source terms on interface boundaries. You have to put it on the boundary face, not the interface object.

Pled · April 4, 2019, 07:31

i will try the option of defining a thin subdomain for the thin surface,
since CFX does not allow the modeling of both an interface and a boundary on the same surface.

Thanks for your help Glenn!

ghorrocks · April 4, 2019, 07:45

Quote:

since CFX does not allow the modeling of both an interface and a boundary on the same surface.

That is not what I said. I said to put a source term on the interface boundary face which is one side of the interface.

There is no such thing as a source term boundary condition - you apply source terms as additional terms on existing domain features.

Pled · April 4, 2019, 07:53

But interface's sides also do not allow momentum sources, only continuity sources.

ghorrocks · April 4, 2019, 18:22

OK, thanks for that. I was not at my workstation so could not check that.

In that case the thin subdomain might be the best way forward.

April 3, 2019, 09:57	Modeling of conditioned flow of interfaces	#1
Pled Member Dimitrios S. P. Join Date: Jan 2018 Posts: 63 Rep Power: 9	Hello everyone. Here is another question. My problem is that I have liquid flow in two domains that have a common interface. The interface allows a mass flow to one direction which is analogous to the wall shear stresses that are applied to it. How can I model it in CFX, since I cannot write any conditional flow.

April 3, 2019, 20:13		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,011 Rep Power: 146	Have you looked at the options available to interfaces? You can specify a mass flow rate at interfaces, and you could make that a function of wall shear stresses or other variables. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 4, 2019, 06:24		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,011 Rep Power: 146	Then maybe make it a standard conservative connection, but use a momentum source term to control the flow locally as a function of anything you like. Pled likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 4, 2019, 06:59		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,011 Rep Power: 146	The thin subdomain can work. I can't check now, but I thought you could put source terms on interface boundaries. You have to put it on the boundary face, not the interface object. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 4, 2019, 18:22		#10
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,011 Rep Power: 146	OK, thanks for that. I was not at my workstation so could not check that. In that case the thin subdomain might be the best way forward. Pled likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 4, 2019, 04:41		#3
Pled Member Dimitrios S. P. Join Date: Jan 2018 Posts: 63 Rep Power: 9	Yes, but this applies an equal distributed mass flow to the interface, not an variable one.

April 4, 2019, 06:42		#5
Pled Member Dimitrios S. P. Join Date: Jan 2018 Posts: 63 Rep Power: 9	This would have been a good solution, if cfx had enabled an option of momentum source in interfaces. Unfortunately, cfx fails to my expectations again. What do you thing of the idea of creating a thin subdomain, instead of just a surface, and apply in it momentum sources?

April 4, 2019, 07:31		#7
Pled Member Dimitrios S. P. Join Date: Jan 2018 Posts: 63 Rep Power: 9	i will try the option of defining a thin subdomain for the thin surface, since CFX does not allow the modeling of both an interface and a boundary on the same surface. Thanks for your help Glenn!

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