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Old   September 8, 2010, 13:26
Smile Boundary Conditions. Simulation cylinder.
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Hello! I just started with OpenFOAM.
I use version 1.7.0. I'm trying to simulate a cylinder in which the laminar (or turbulent) incompressible fluid flow.
And the bottom of the cylinder rotates. Like this:



What is the boundary condition I set on the bottom and how to do it?
I would be grateful for any assistance conditional. Maybe someone has already done this?
Sorry for my English

A! And what solver shall i use?
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Old   September 11, 2010, 12:30
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Surely no one can help? It's very, very important to me, please...
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Old   September 17, 2010, 08:42
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Hi David and welcome! Hope to be not too late...
Quote:
Originally Posted by davidmd View Post
what solver shall i use?
Everything depends on what simulation you want to perform. I guess you want a steady state laminar or turbulent simulation. In that case I would use simpleFoam.
Quote:
Originally Posted by davidmd View Post
And the bottom of the cylinder rotates. What is the boundary condition I set on the bottom and how to do it?
If you wants that the cylinder bottom is the only rotating surface, than I would apply a rotatingWall BC. Search in the forum for the way to apply it.
Enjoy

mad
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Old   September 19, 2010, 10:04
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Thank you very much, maddalena, I built something like the geometry and boundary conditions, but I used iсoFoam not simpleFoam. What is the difference between them?
I apologize for maybe a stupid question. I just sooo hard to read literature in English
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Old   September 20, 2010, 03:01
Default simpleFoam v.s. icoFoam
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Hi David
How are you? I hope you are doing very well.
As you can see in the source of the solvers icoFoam is a transient solver for incompressible, laminar flow of Newtonian fluids and simpleFoam is a steady-state solver for incompressible, turbulent flow.
Good luck
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Old   September 23, 2010, 08:42
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Now I'm faced with this problem. I can not define the boundary condition at the upper edge of the cylinder (i mean the top sureface of my fluid). Maybe someone knows how to do this? Uz = 0, dUx / dx = 0, dUy / dy = 0

Last edited by davidmd; September 23, 2010 at 09:16.
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Old   September 23, 2010, 08:47
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Hi, ata!
Thank you for help, I hope you are all well too!
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Old   September 23, 2010, 10:14
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I'm trying to simulate simple mixer. It looks like cylinder with rotating bottom and open top filled with fluid. The other cylinder is inserted into the first.
So something like this:








So, on the walls of this cylinders i set the fixedValue BC On the bottom - rotatingWallVelocity.
And to top I want to set the boundary condition such as on the surface of the liquid ... At first I tried to do zeroGradient boundary condition. But then it turns out like this:


It turns out that the fluid enters the center and comes out at the edges, but this is not correct.
I thought that it was possible to establish a boundary condition like Uz = 0 Ux = dUx / dx Uy = dUy / dy

Maybe i need another BC... I don't know. The main thing that it was just on the surface of the liquid.

Once again: sorry for my English :-)
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Old   September 23, 2010, 10:48
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Mmm...
I am still confused by your geometry...
there are two cylinders, one inside the other, filled with fluid. The external one has a rotatingWall BC, while the internal one is fixed. The bottom of the internal cylinder is open. You want to study the effect of the bottom surface rotation of the external cylinder into the fluid. Am I right?
What about your pressure BC?
As a first idea, I would use an inletOutlet BC for U and a fixedValue for p. But not sure about that.

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Old   September 23, 2010, 14:34
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maddalena, you are right!
My preasure BC is set to fixedValue and it is 0...
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Old   September 23, 2010, 15:16
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So, this is fine:
Quote:
Originally Posted by davidmd View Post
My preasure BC is set to fixedValue and it is 0...
if you fix pressure, you cannot fix velocity, and your gradient should be specified instead. I would use an inletOutlet with an inletValue (0 0 0): it will behave as a fixedValue on the inner cylinder and as a zeroGradient on the fluid between the two cylinder.
what you think about that?

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Old   September 24, 2010, 03:33
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You mean the boundary condition inletOutlet with inletValue (0 0 0) on the upper surface of the cylinder?
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Old   September 24, 2010, 03:57
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Quote:
Originally Posted by davidmd View Post
You mean the boundary condition inletOutlet with inletValue (0 0 0) on the upper surface of the cylinder?
Yes, that one. Please report if you have different ideas or if you can find a solution.
cheers

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Old   September 24, 2010, 11:52
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Quote:
Originally Posted by maddalena View Post
Yes, that one. Please report if you have different ideas or if you can find a solution.
cheers

mad
Wow! It works exactly as I have! maddalena, thank you very much! It's great!!! I never would have guessed! :-)
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Old   September 26, 2010, 07:44
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Quote:
Originally Posted by davidmd View Post
Wow! It works exactly as I have! maddalena, thank you very much! It's great!!! I never would have guessed! :-)
That is nice! Happy to be useful!
Cheers

mad
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Old   October 6, 2010, 09:42
Default cylindrical shapes
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Hi guys
since you worked with cylindrical shapes i thought you might help me please

i need to do a flow between two parallel disks the bottom is stationary and the on eon top rotates with a certain omega.

How to draw?

Help please, and what about the BCs?

thanks a lot
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Old   October 6, 2010, 14:49
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Hi, T.D.!
I don't understand your geometry
maybe you can draw it?
It's very difficult to me to wrote on english
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Old   October 6, 2010, 17:15
Post Drawing attached
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hi
this is the drawing attached

thanks a lot
Attached Images
File Type: jpg flow.JPG (11.9 KB, 33 views)
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Old   October 6, 2010, 18:31
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i'm not sure, but you probably should use BoundaryFOAM
And create such a geometry will be no problems. If you want me to send you an example of my case with rotating bottom. But you have to fundamentally alter it.
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Old   October 7, 2010, 02:33
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Hi T.D.
How are you brother? I hope you are doing very well.
May be you can use gambit for mesh generation.
Good luck
Best regards

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