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how to create multiple fluid zones and an interface

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Old   April 9, 2015, 10:41
Question how to create multiple fluid zones and an interface
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hi friends,

how can i create two fluid zones of water and air with an interface separating them in a single domain as shown in the attached pic; so that i can study the effect of flowing water on the motion of entrapped air within the cavity.

1.how can i create this zones using design modeller and ansys mesher? should i create and mesh the zones separately?

2.how can i form the interface?

3.should i go for multiphase modelling like VOF and patch the regions?(here the interface is fixed)
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File Type: jpg interface.jpg (21.0 KB, 21 views)
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Old   April 9, 2015, 13:25
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the interface should follow from the motion and interphase forces right? If you use VOF, the shape of the interface should result from your calculation, not the other way around.
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Old   April 9, 2015, 14:42
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thank you for your response.

as far as i know, in VOF interface shape evolves from solution naturally; but before that as a first step i have to study the stream lines of air inside the cavity by solving the equations in water and air zones and by coupling their interfaces with the assumption that the interface position and shape are known already.

all i want to know is how to create these two cell zones of different fluids with a common interface in ANSYS FLUENT.

hope you can help me.....thanks in advance....
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Old   April 9, 2015, 19:30
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Create two cell zones by generating a multiblock mesh, then allocate the water phase to the upper block and the air phase to the lower block.
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Old   April 9, 2015, 22:23
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thank you.....i shall try it.......
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Old   April 10, 2015, 04:07
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Quote:
Originally Posted by `e` View Post
Create two cell zones by generating a multiblock mesh, then allocate the water phase to the upper block and the air phase to the lower block.
since i m just a biginner i m struggling with this problem. i couldnt find any options like multiblock meshing . instead i saw a cell zone separtion method in fluent in which a single cell zone can be separated into multiple zones by separate>cells option (before this the region is marked using adapt>mark).

in this method i could create 2 different fluid zones in fluent but it creates additional interior surface bodies and additional wall bodies(may be becoz the wall come in contact with both fluid zones). i tried to merge the interiors to form a single interface but its not working........

exactly what i need is in the boundary condition panel i need

1. inlet and outlet
2.wall boundaries
3. an interface(on which i have to apply some conditions later)
4. 2 fluid zones(air and water)

can plz help me by suggesting the methods i should follow

1. in ansys design modeller to create the geometry
2. in ansys mesher to create multiblock mesh
3. in fluent to create the common interface as a single entity
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File Type: jpg interface.jpg (24.2 KB, 9 views)
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Old   April 10, 2015, 05:26
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Dividing the geometry I'd do in design modeler. You already drew the interface in there, so it seems you already did this. In meshing, you can just mesh the domain, and under named selections; create one body selection for the water zone, and one for the gas zone. There are no issues there.

In FLUENT, you can then initialize one zone with gas, one with water. But as soon as you start your calculation, the interface will start to move. And this is not what you want I think?
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Old   April 10, 2015, 06:46
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CeesH is correct, you should create this multiblock body at the geometry stage (DesignModeler). Ensure you have not merged these two zones together (use 'Add Frozen' instead of 'Add Material'), and remember to create a new part from these bodies (this action instructs Meshing/Fluent to connect/interface the two zones instead of treating them as separate domains). If you're having troubles, post a screenshot of your geometry in DesignModeler including the tree window.
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Old   April 12, 2015, 23:24
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thanks a lot for your suggestions........

i could create two different cell zones with an interior zone in betwwen them....

is there any way to apply boundary conditions on the interior zone using some UDF ?
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Old   April 12, 2015, 23:41
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Quote:
Originally Posted by CeesH View Post
Dividing the geometry I'd do in design modeler. You already drew the interface in there, so it seems you already did this. In meshing, you can just mesh the domain, and under named selections; create one body selection for the water zone, and one for the gas zone. There are no issues there.

In FLUENT, you can then initialize one zone with gas, one with water. But as soon as you start your calculation, the interface will start to move. And this is not what you want I think?
hi friends,

as i mentioned earlier as a second stage i would like to model the natural evolution of the interface due to the effect of
1.surface tension forces
2.contact angle of the surface
3.pressure difference across the interface


how can i model it to incorporate the above effects?

can anybody suggest a skeleton for the model?

the expected shapes of interface under different flow conditions are as shown in fegure....

i can explain more if u need more details.........
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File Type: jpg diff interfaces.jpg (19.6 KB, 2 views)
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Old   June 6, 2015, 03:30
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Quote:
Originally Posted by josephmp View Post
hi friends,

how can i create two fluid zones of water and air with an interface separating them in a single domain as shown in the attached pic; so that i can study the effect of flowing water on the motion of entrapped air within the cavity.

1.how can i create this zones using design modeller and ansys mesher? should i create and mesh the zones separately?

2.how can i form the interface?

3.should i go for multiphase modelling like VOF and patch the regions?(here the interface is fixed)
"How to Setup Two Fluid System in Fluent"

http://www.cfd-online.com/Forums/mem...luidsystem.png


I have exactly same problem and is having trouble to find ways around. It is a Two Fluid Zone but separated by a Orifice Plate.

Fluid Two is in Top Zone while Fluid One is in Bottom Zone. Both Fluid are separated by a Orifice Plate in middle. In Zone one, fluid one never mixes with fluid two. While fluid one is pumped into zone two which is filled with fluid two, where both fluids mixes and eventually exit through an outlet at the top of zone two.

Both Fluids are Separated.

Fluent CFD does not allow me to setup Two Independent Fluids. It allows a Mixture of Two Fluids only. I don't want fluid two in Zone One. While zone two is only place where both fluids mixes(Two Phase System).

Can some one tell me how to setup two fluid system. Each fluid have their own phases.

Thanks in advance.

Shane
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