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javorpanev
Posts: 11
Registered: ‎10-18-2012

Gravitational Filter Simulation

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07-31-2013 02:17 AM

Hi, I would like to simulate the motion of fine particles of diameter 0.1-1mm within a large container. I have calculated their terminal velocity from Stocks equation to be around 0.5-2 mm/s. CFD simulation returns results of flow velocity varying from 50mm/s at the outlet/inlet and <10mm/s within the volume.

 

I want to model the motion of the particles using mass tracers but I am confused what values to use for calculating the drag coefficient. Due to the low velocities the Reynolds number appears to be around 0.01 to 0.001 ( I used formulas from http://wikihelp.autodesk.com/Simulation_CFD/enu/2014/Help/0360-Learning360/0481-Referenc481/0503-The... 0). Textbooks suggest Cd for such Reynolds numbers to be from 100-1000. Having that in mind I basically adjusted the a,b,c coefficients to return values for Cd in that range. Is this approach correct?

 

Also what is the significance of "time step size"? I can't find any explanation about it.

 

Thanks,

Yavor Panev

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