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simulating solid granules in CFX

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Old   January 19, 2015, 17:11
Default simulating solid granules in CFX
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Sara S.
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Hi all,

I am trying to simulate the following problem in CFX 15.0.

500 granules (PE is the material) of 6mm diameter and overall weight of 500gr are sitting (floating) in water. At some point water starts to flow and with it these granules also flow. I will have turbulent flow.
I know that in FLUENT this can be done with DPM. and I am trying to use particle transport solids in CFX (to simulate Lagrangian particle tracking) but I don't know how I can start with granules sitting (floating in water) not injecting granules in the domain.

Can you give me some hints?

Thank you,
Sara
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Old   January 26, 2015, 08:29
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Hi Sara,

I am also facing the same problem. In my case I want to distribute some particles on a solid surface and investigate the effect of jet impingement. Did you make any progress so far?

Ocea
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Old   January 26, 2015, 17:21
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Glenn Horrocks
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Sara's question sounds possible in CFX with little difficulty. Have you done the tutorials? Or what specific thing is not working.

Ocea's question is a little more difficult - what is holding the particles there before the jet hits? Are they just resting there under gravity.
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Old   January 29, 2015, 11:00
Default solid granules in fluid, no injection
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Sara S.
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Glen,

Imagine I have a tank full of water (open to atmosphere) and the PE granules are sitting in this tank. We have a reservoir of water (again open to atmosphere) which is a little higher than the tank. The simulation starts when the water reservoir's opening to tank opens and allows water flow into the tank and then moves the granules.
So the start of the simulation is the point that these granules are already in the water and the opening form reservoir to the tank opens.

My problem is I don't know how I can simulate these granules without defining an injection point. In my simulation so far, the granules start to be injected in the water from a point with a certain velocity and mass flow.
I don't know how I can start from the point that some certain number of granules are already sitting in the water.

I did not find any tutorial related to this problem. Could you suggest any?

thank you,
Sara
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Old   January 29, 2015, 17:06
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Glenn Horrocks
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Just looked in the documentation - it looks like you cannot specify initial locations for particles.

So I can think of a few work-arounds:
* You could do an initial simulation where you inject the particles and allow them to settle. Then you use this as initial condition for the actual run.
* You use user fortran to specify a user injection location at time step 0 with zero velocity and place them in the region you want them to start in.

And another thought: This model may be more suited to a eularian particle model simulation. Then the initial condition is easy to specify, and you can also set maximum packing fractions and many other parameters which will probably be useful which are not available in the lagrangian model.
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Old   March 9, 2020, 22:03
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Basivi Reddy
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I have a similar problem, any progress or any suggestions about defining solid particles resting in a cylinder?
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Old   March 10, 2020, 06:09
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I think my post #5 explains it, don't you?

Note you cannot model particles resting on each other in CFX. CFX only supports very limited particle to particle interaction. You will need a Eularian model or a DEM model to model that.
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Old   March 11, 2020, 20:00
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Thanks for the reply, I can able to do it in Fluent by using Eulerian model.

Reference: https://www.youtube.com/watch?v=W2y9rKXapds
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