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Rotatory cillindrical geometry

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Old   September 26, 2007, 06:33
Default Hello, I am new in OpenFOAM
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Miquel Vinya
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Hello,

I am new in OpenFOAM and I am trying to simulate a bathtub vortex in a rotating container.

I have done my geometry in workbench, meshed with cfx mesher, converted to fluent mesh and imported with fluentmeshtofoam.

Now I am working with FoamX introducing data for the simulation. My goal is to obtain the vortex profile such as the experiment made by Andersen, Bohr, Lautrup et al in "The bathtub vortex in a rotating container".

The geometry is a cillindrical body cut in a 1/12 part. There is an input at the bottom and the top side is open to atmosphere. I use interFoam for solving the interphase.

I have 2 symmetry planes and I try to introduce te constraint of rotating matter (at 6 rpm).

How can I do this?

Thanks for your attention!
Miquel
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Old   September 26, 2007, 07:03
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Miquel Vinya
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Old   September 27, 2007, 05:19
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Paul Mauk
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Hi,

I'd like to know too: is it possible, to create a rotary motion in OpenFoam?
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Old   September 27, 2007, 05:25
Default I don't see what the problem w
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Hrvoje Jasak
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I don't see what the problem would be: in the case above all you need to do is to specify non-zero tangential velocity on the rotating wall.

Of course, there is a ton of other (more complex) things you can do with OpenFOAM, including multiple rotating reference frames, mixer-type sliding meshes or goneral coupled mesh interfaces.

Hrv
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Old   September 27, 2007, 05:49
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Miquel Vinya
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Hello,

Thanks for your attention. What I am trying to say is that I don't know where must I specify the tangential velocity in FoamX (under interFoam). I've been looking through forum and User Guide and I don't know how to do it...

Another question is about how can I fix a mass flow at the inlet equal to the outlet (initialisation).

Thank you very much,
Miquel
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Old   September 27, 2007, 10:38
Default Hi Miquel I'm not sure I got
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Cedric DUPRAT
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Hi Miquel
I'm not sure I got what you want but in this thead : http://www.cfd-online.com/OpenFOAM_D...4.html#POST914 you can find some tips (code) to impose a rotating wall.
Maybe, using the same idea, you can impose a tangential velocity, can't you ?

Hope it helps you
Regards,

Cedric
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Old   October 1, 2007, 04:03
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Miquel Vinya
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Thanks Cedric; I will take a look on it.

And please answer me another question: Is it better to make a cut of 1/12 part of the cillinder with 3D geometry or make a 5 cut with 1 cell of profundity?

Thank you,
Miquel
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Old   October 1, 2007, 04:15
Default Hi Miquel, It depends what
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Hi Miquel,

It depends what you plan to do with your (calculation).
for exemple, turbulent model ?, which one ?:
- RANS : a cut is enought
- LES : all the geometry have to be built
then, the difference between 1/12 and 5 ... I don't wan't to give you wrond advise ... maybe check the litterature.
What do you plan to do with your pipe ? how do you plan to do that ?

Regards,

Cedric
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Old   October 1, 2007, 04:36
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Miquel Vinya
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Thanks Cedric,

I am reproducing an experiment ("The bathtub vortex in a rotating container", J. Fluid Mech. (2006), vol. 556, pp. 121–146.) for observing the formation of a bathtub vortex in a vertical cillinder.

1. There is a hole at the bottom. Water falls due to gravity.
2. The cillinder rotates at a rate of 6 rpm and it moves the matter of water for creating the vortex
3. There is an inlet at the bottom-side of the cillinder. The mass flow at inlet is equal to the outlet mass flow for conserving the total volume
4. The top of the cillinder is open to atmosphere

My goal is to obtain the profile of the vortex and compare with this:


I have turbulent flow for a 2-phase system, but all I want to solve is the interphase. For this reason my mesh is more concentrated in the zone where the vortex is created.

I haven't found any example of angular moving walls in the tutorials and I feel lost.

Best regards,
Miquel
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Old   October 1, 2007, 05:10
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Cedric DUPRAT
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Hi again,

don't hesitate to look in the forum, we can find every thing. here is an other thread on rotating flow motion:
http://www.cfd-online.com/OpenFOAM_D...html#POST13810
cylindrical coordinate are available in OF (not trivial according to me), to do an angular moving wall, you have first to find the moving wall and then to fix a velocity at the wall (cavity tutorial). the only difference is that you have to define an other coordinate (not X, Y, Z but r, teta, Z ).Check these codes (in that thread) and adapte them to your case.

regards,
Cedric
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