# question about free surface-multiphase simulation

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 March 30, 2011, 11:30 question about free surface-multiphase simulation #1 New Member   harry Join Date: May 2009 Posts: 29 Rep Power: 10 Hi all, I'm running a multiphase simulation of air and water, both defined as continuous fluid, which are trapped in an enclosed chamber under rotation using cfx. I use inhomogeneous and standard free surface model , laminar condition. In the fluid pair models, define free surface for the interphase transfer. And there is a drag force and coefficient option for the momentum transfer, and I just leave the default unchanged. Chamber shape: block. Initial condition: t=0, force the water takes 3/4 volume of the chamber, and air takes the rest 1/4 volume. And there is distinct interface between air and water. Boundary condition: walls and symmetry ( no inlet and outlet) Once t>0, the chamber is under rotation. I'm interested in the interface change between air and water due to the rotation. There is still distinct interface between air and water during rotation, however, to my surprise, I found the volume of air is increased to be more than 1/4, and volume of water is reduced given the results I obtained. Could anyone give me any suggestions please? Any problem with the model? Thanks.

 March 30, 2011, 19:36 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,863 Rep Power: 107 Please post some pictures of what you are seeing. Also why are you using the inhomogenous model? Do you expect foam or bubbles?

March 31, 2011, 00:45
#3
New Member

harry
Join Date: May 2009
Posts: 29
Rep Power: 10
Hi Ghorrocks,

Thanks for your reply. I just attached some pictures including the results and pre setting up, could you please take a look at them? Thanks.

Since in cfx, they define Inhomogeneous is the general case of multiphase flow, where each fluid has its own velocity field, and so on. I think air and water in my case should have their own velocity field, so I use the option. Thanks.
Attached Images
 fliud pair.jpg (39.0 KB, 22 views) multiphase.jpg (32.4 KB, 23 views) t=0.jpg (33.5 KB, 27 views) t=1s.jpg (35.4 KB, 22 views) t=1s (3d view).jpg (48.9 KB, 28 views)

 March 31, 2011, 06:37 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,863 Rep Power: 107 What is this trying to model? I still do not understand. Why do you think air and water should have their own velocity field?

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