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OpenFOAM - mixing tank simulation using dynamic mesh

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Old   April 17, 2019, 10:48
Default OpenFOAM - mixing tank simulation using dynamic mesh
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Hi, all. I am simulating a mixing tank, just like the one in the following video clip:

https://youtu.be/W96Daf28msY

The simulation is made by OpenFOAM v1712 based on dynamicRefineFvMesh and interDyMFoam as the solvers. kOmegaSST is used as the turbulence model. This is my first time to do dynamic mesh model.

The geometry is very simple, with only a cylinder and a impeller/shaft inside it. There are 3 types of BC: 1. solid walls for cylinder circumference and bottom, impeller and shaft, 2. AMI for the interface between moving and non-moving meshes, and 3. atmosphere at the top. The dynamicMeshDict specifies a 6.28 rad/sec rotation.

I used cfmesh to do the meshing and was sucessfully run the model with dynamic mesh. However, I wouldn't simulate the drop in water surface due to the swirling flow, even up to the simulation time more than 20 sec.

The wall and AMI BCs are straight forward, and I think it should not be any problem. For the atmosphere, I used pressureInletOutletVelocity for U, totalPressure (0) for p_rgh and inletOutlet (0) for alpha.water. any expert can comment on my BCs?

Are there any other possible reasons?

Hope some experts here can help!!
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Old   April 21, 2019, 21:00
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Hisham Elsafti
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Hi foamF

It is most likely a problem with the settings of your BCs. It is hard to know what exactly the problem is without seeing the case. If you can pack it and upload it somewhere, I am sure you will get quick response.

Best regards
Hisham
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Old   April 23, 2019, 06:08
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Thanks. I am still doing some trials.

Preliminarily, it is a matter of wrong BC. After using movingWallVelocity for the solid walls - impeller and shaft (located inside cellZone with rotation as specified in dynamicMeshDict), the velocity field looks more reasonable and the water surface starts to drop.
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