specifying interface boundary condition

cprasad111 · May 19, 2011, 04:34

Need help !!

I need to specify the following interface boundary condition :

(viscosity1)*d(velocity1)/d(x)=(viscosity2)*d(velocity2)/d(x)

where 1 and 2 represents two domains containing different fluids
the interface is planer

ghorrocks · May 19, 2011, 08:44

Is the x direction prependicular to the surface? Then isn't this simply the shear stress on one side of the interface is the same as the other?

I cannot think of an easy way to implement this with two domains. You could do it as a multiphase free surface model, but freeze the volume fraction field using expert parameters. This would match the shear stresses across the interface.

cprasad111 · May 19, 2011, 12:15

yes, the x-direction is perpendicular to the interface
Actually, I am new to this software, please explain in detail

Thank you for the reply

ghorrocks · May 19, 2011, 19:48

Set up a multiphase simulation with one fluid as one phase and the other fluid as the other phase. Use a single domain. Set an initial conidtion on the volume fraction for the location of the two fluids. Use the expert parameter "solve volume fraction" set to false so the solver does not update the volume fraction field.

But I suspect the interface will actually move, so you could probably leave the volume fraction on as default and let the solver sort it out.

Do the CFX tutorials on free surface flow to understand setting it up.

cprasad111 · May 31, 2011, 02:48

Multiphase models take 2-3 days to solve just momentum equations. And here we have to solve momentum, mass tranfer and reaction equations too. So, I am trying it in single phase

Actually I am using single phase model with two domains. And the boundary condition is to given at the interface of the two domain.
Could you please help on this.

ghorrocks · May 31, 2011, 09:18

That's why I say to freeze the volume fraction equation and the run time will not be too much longer than a single phase model.

cprasad111 · June 1, 2011, 08:57

Is it posssible to run a simulation including mass transfer and reaction in free surface model (multiphase) in CFX

ghorrocks · June 1, 2011, 19:24

In general yes, but I do not know specifically what you are doing so cannot say for sure on your case.

May 19, 2011, 04:34	specifying interface boundary condition	#1
cprasad111 New Member Churamani Prasad Join Date: May 2011 Posts: 16 Rep Power: 15	Need help !! I need to specify the following interface boundary condition : (viscosity1)d(velocity1)/d(x)=(viscosity2)d(velocity2)/d(x) where 1 and 2 represents two domains containing different fluids the interface is planer

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Problem with Interface Boundary Condition	tos	FLUENT	0	April 4, 2010 09:11
Boundary condition at the interface of two fluids	bhaskar	FLOW-3D	1	May 22, 2009 17:34
how to set up a wall boundary condition according to calculated wall shear stress?	gameoverli	OpenFOAM Pre-Processing	1	May 21, 2009 09:28
interface boundary condition definitions?	Skander	FLUENT	1	November 2, 2006 16:47
[Commercial meshers] Trimmed cell and embedded refinement mesh conversion issues	michele	OpenFOAM Meshing & Mesh Conversion	2	July 15, 2005 05:15

May 19, 2011, 08:44		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Is the x direction prependicular to the surface? Then isn't this simply the shear stress on one side of the interface is the same as the other? I cannot think of an easy way to implement this with two domains. You could do it as a multiphase free surface model, but freeze the volume fraction field using expert parameters. This would match the shear stresses across the interface.

May 19, 2011, 12:15		#3
cprasad111 New Member Churamani Prasad Join Date: May 2011 Posts: 16 Rep Power: 15	yes, the x-direction is perpendicular to the interface Actually, I am new to this software, please explain in detail Thank you for the reply

May 19, 2011, 19:48		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Set up a multiphase simulation with one fluid as one phase and the other fluid as the other phase. Use a single domain. Set an initial conidtion on the volume fraction for the location of the two fluids. Use the expert parameter "solve volume fraction" set to false so the solver does not update the volume fraction field. But I suspect the interface will actually move, so you could probably leave the volume fraction on as default and let the solver sort it out. Do the CFX tutorials on free surface flow to understand setting it up.

May 31, 2011, 02:48		#5
cprasad111 New Member Churamani Prasad Join Date: May 2011 Posts: 16 Rep Power: 15	Multiphase models take 2-3 days to solve just momentum equations. And here we have to solve momentum, mass tranfer and reaction equations too. So, I am trying it in single phase Actually I am using single phase model with two domains. And the boundary condition is to given at the interface of the two domain. Could you please help on this.

May 31, 2011, 09:18		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	That's why I say to freeze the volume fraction equation and the run time will not be too much longer than a single phase model.

June 1, 2011, 08:57		#7
cprasad111 New Member Churamani Prasad Join Date: May 2011 Posts: 16 Rep Power: 15	Is it posssible to run a simulation including mass transfer and reaction in free surface model (multiphase) in CFX

June 1, 2011, 19:24		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	In general yes, but I do not know specifically what you are doing so cannot say for sure on your case.