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Old   April 23, 2019, 06:57
Default Request help for Dynamic Mesh
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Joe lee
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I have a simulation that requires dynamic mesh, but I cannot find adequate information of how the whole setup for dynamic mesh. I am new to openFoam, so most of the tutorials I found online is not understandable for me. They are either in lack of detail, or do not have enough guidance. Therefore, I would like to ask for some clear procedure for a dynamic setting.

Below is my simulation requirement:



I need to simulate an object moving from position A to D, passing B and C. In another word, I would like the object to rotate about the axis R_hat. The fluid domain does not have any inlet velocity. It is stationary at the beginning, and the motion of the object would induce the fluid flow inside this domain. Also, the blue arrows indicate the direction that the object is heading to at that moment.

I have set up my dynamicMeshDict as follow:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  6
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dynamicFvMesh  dynamicMotionSolverFvMesh;

motionSolverLibs ("libfvMotionSolvers.so");

motionSolver   solidBody;

cellZone  model;

solidBodyMotionFunction rotatingMotion;

origin  (-24636.7487 205.267 976.917);
axis    (0 1 0);
omega   0.4986;
Yet after setting up the dynamicMeshDict, I do not know what should be done next.


I am studying the propeller case, but I have totally no idea of what those cellzone, toposet, etc. are. Could anyone please give me a guideline on how to perform such a simulation? Thanks a lots!!!!!!!!!
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Old   April 24, 2019, 03:40
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Does anyone have any idea?

Last edited by Tobi; April 24, 2019 at 08:43.
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Old   April 24, 2019, 08:46
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Hi,

if the rotation of the sphere is on a circle, you could make the following:

a) build the fluid domain
b) create the sphere at position A and export it as STL
c) create a cylinder that encloses the sphere and does have the centerline at your centerline you want to have the rotation
d) use snappyHexMesh to i) cut out the sphere and ii) use the cylinder to build a cellZone and faceZone

After that, you can use the faceZone to split the faces (build baffles) and then you can use the cellZone to rotate all cells that are enclosed by the cylinder.
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Old   April 24, 2019, 09:18
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Quote:
Originally Posted by Tobi View Post
Hi,

if the rotation of the sphere is on a circle, you could make the following:

a) build the fluid domain
b) create the sphere at position A and export it as STL
c) create a cylinder that encloses the sphere and does have the centerline at your centerline you want to have the rotation
d) use snappyHexMesh to i) cut out the sphere and ii) use the cylinder to build a cellZone and faceZone

After that, you can use the faceZone to split the faces (build baffles) and then you can use the cellZone to rotate all cells that are enclosed by the cylinder.
Hi Tobi, thank you very much for your response.
I have done a) and b).
And for c), do you mean something like the image below:

Where the red cyclinder surround all the position of the sphere that it may move along, and the red centerline (C_hat) of the red cyclinder is collinear with the center of motion (R_hat)?

Also, for part d), I do not understand how to cut out the sphere and use the cylinder to build a cellZone and faceZone. Is these done in a custom Dictionary other than the snappyHexMeshDict? or does it use something like toposet?

And for:
Quote:
After that, you can use the faceZone to split the faces (build baffles) and then you can use the cellZone to rotate all cells that are enclosed by the cylinder.
Could you please explain briefly how could I perform this step? I have never perform such a manipulation.

Thank you very very much!
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Old   April 26, 2019, 14:28
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Quote:
Originally Posted by Jinjolee View Post
Hi Tobi, thank you very much for your response.
I have done a) and b).
And for c), do you mean something like the image below:

Where the red cyclinder surround all the position of the sphere that it may move along, and the red centerline (C_hat) of the red cyclinder is collinear with the center of motion (R_hat)?

Also, for part d), I do not understand how to cut out the sphere and use the cylinder to build a cellZone and faceZone. Is these done in a custom Dictionary other than the snappyHexMeshDict? or does it use something like toposet?

And for:

Could you please explain briefly how could I perform this step? I have never perform such a manipulation.

Thank you very very much!
Could anyone briefly explain how to perform these? Many thanks
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Old   April 29, 2019, 11:07
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Is there any tutorial or example that may help?
Still got no clue on the facezone, cellzone, baffle, AMI stuff.
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Old   May 5, 2019, 13:30
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I am still getting trouble on this issue, would anyone like to help? Thanks!
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