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Old   July 18, 2016, 07:41
Default Suggest physics models
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sriram
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Hi evry1
Im working with solid particles suspended in water flow through pipes.Note:The solid doesnt dissolve in water...
Under what category this comes??
What kind of physics model must be given?
Can i change the water standards like density??
I am finding clueless...even the star ccm+ tutorial guide shows legrangian laden flow,Eulerian laden flow with rotating walls.

I tried eulerian multi phase,eulerian segregated models..
But i kept gettin AMG solver divergd.

Not very much familiar with CCM+ just startd using

Thank u
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Old   July 18, 2016, 10:47
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You can use any of the multiphase methods. If the number of particles are less, I would go for lagrangian.

You can change properties of water. It should be under Conitnua > Physics.

Try reducing the relaxation factors to avoid divergence, atleast thats what help me mostly if my solution diverges from the very beginning..Also make sure your mesh size and time steps are appropriate.

hope that helps
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Old   July 19, 2016, 01:28
Default still diverging
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thank u
but its still diverging...how to set time step...i've right clicked>continua i dont find casting physics option as given in the tutorial guide.
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Old   July 19, 2016, 02:30
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can u suggest me the list of physics models to be used...i think that s where im making mistake
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Old   July 19, 2016, 02:56
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I was also thinking Lagrangian or DEM but maybe a better starting point is the tutorial for fluidized bed. Your particles laminar and liquid is turbulence, I think you wanted this also.

Keep things very simple in the beginning, use the minimum amount of models in the beginning, for example in the interaction use only drag and a constant interaction length scale. Perhaps steady-state, use constant properties, try to get a stable run using minimum amount of models.


You are most likely going to have to reduce the relaxation factors or time step,

Might even want to try laminar for the liquid phase as well.
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Old   July 19, 2016, 05:40
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thank u
i have changed the relaxation factors values as mentioned in the tutorial guide,now it converges.
But the iteration doesn't stop once the maximum step is achieved.Why is that?
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Old   July 19, 2016, 05:50
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Can you post a screenshot of your 'stopping criteria' tree ? (with the nodes expanded of course)
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Old   July 19, 2016, 06:37
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i have attached the images
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Old   July 19, 2016, 08:48
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Are you running a steady state simulation ? I think no of time steps would matter only for transient simulations.
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Old   July 19, 2016, 09:31
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yes it is a steady state.....i ran another simulation and it stopped correctly at the stopping criteria...so the relaxation factor change worked it seems...coz the simulation is not getting diverged
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Old   July 19, 2016, 09:53
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i ran an earlier divergence occurred simulation...with changing the relaxation factor..but error occurs again....
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Old   July 20, 2016, 03:31
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Please be more clear, as I understand, you had a solution that wasn't diverging after changing relaxation factors. But then what did you change so that the solution started diverging ?

Keep your simulation as steady/unsteady and then change other simulation parameters one by one, if you change many things at once, it would be hard to identify what causes problems exactly.
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