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Swapnil November 28, 2002 21:32

Thin film flow in triangular duct
Hi everybody,

I am trying to model COUNTERCURRENT two-phase flow in triangular duct. The liquid flow is in the form of thin film. I have two questions related to this

1)Since the liquid flows in the form of thin film it will occupy very small part of the cross-section. How to model the thin film?

Since the flow is countercurrent, the liquid will enter at the boundary which serves as the outlet for the vapor phase. Now at this boundary, a small portion will be occupied by the liquid (entering into duct) and rest will be occupied by the gas (outlet for gas). How to define this type of boundary condition?

Actually, my final aim is to model the two-phase flow in a network of triangular ducts crossing each other at 90 degrees. As the base case, i am starting with single duct.



Swapnil December 2, 2002 15:16

Re: Thin film flow in triangular duct
Will any body help me!

Astrid December 3, 2002 17:19

Re: Thin film flow in triangular duct
I will give it a try.

- I think you can use the 'opening' boundary condition as flow can come in and go out of the domain. Thus your gas can come in and your liquid can go out at the bottom, and at the top the other way around.

- How thick will you liquid film be? I think you can describe the film using multiphase flow. I suspect the conditions in thin film will be laminar. The whole case can be done easily if your gas flow is also laminar. If it is not.... than you are in trouble.


Swapnil December 4, 2002 12:06

Re: Thin film flow in triangular duct
Thanks Astrid,

The Gas flow is turbulent. I am not able to visualize how i can specify the liquid film flow in CFX build. It's a free surface flow problem and in the tutorial only one example for free surface flow is given (flow over a bump). Do you have any example on thin film flow?

Best regards, Swapnil

Astrid December 4, 2002 17:08

Re: Thin film flow in triangular duct
No, I do not have an example. When your gas is turbulent, you will face difficulties in applying the correct boundary layer behavior near the liquid film. I think you have to survey open literarue on this... I have no experience.

For the specification, you have to give a good initial guess for the phase distribution. Also, you have to prescribe the phase distribution over both openings. Ask the helpdesk, perhaps they have more experience..


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