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-   -   transient motion of solid sphere in aflow through pipe (http://www.cfd-online.com/Forums/cfx/113981-transient-motion-solid-sphere-aflow-through-pipe.html)

sajeesh March 2, 2013 12:08

transient motion of solid sphere in aflow through pipe
 
hi,

I am a beginner in ansys ..I am modelling a transient behaviour of solid sphere which is placed in a moving fluid..the solid is taken by the fluid by the drag force..This sphere interact with the fluid and modify the flow field like pressure due to the presence of flow field..finally the the sphere comes to steady state.Which way i should start....any tutorial anybody can suggest....
IS it (i) moving mesh problem or (II) particle tracking (III) or VOF ....i doubt which method i should follow



some body help me...............
thanks



thanks

ghorrocks March 3, 2013 06:27

It could be any of those approaches, and a few more - immersed solid, rigid body, eularian multiphase could also do it.

Can you describe some important parameters (size of particle, how many particles, what is it shape, what is driving it, where it is likely to reach a steady state, density of the particle, ambient fluid etc) and most importantly - why are you doing this model? What are you intending to learn from it?

sajeesh March 4, 2013 07:19

Thank you sir

My channel having dimension 50 micrometer square cross section
My particle is of the size 25 micrometer diameter
The continous fluid is water
the polystyrene bead having density 1060 kg/m3
Inlet mass flow rate of water is 0.833e-6 kg/sec


My problem definition

With out any particle presence the flow through the square channel i simulated. i can find out the pressure drop on both ends of channel and this is simple simulation..then


sir i want to place one polystyrene bead at the inlet of channel..and i want to track the movement of bead.there is coupling of drag force of fluid on the particle and this particle can modify the flow field also.( two way coupling).No gravity effect.
finally at one position the the particle become steady by the two way couplnig.I want to know that position..also i want to find out the extra resistance offered by this particle on the flow at this position..

thanks

sajeesh March 4, 2013 07:20

polystyrene bead is the particle..

Shahr March 4, 2013 12:26

You should use moving mesh, with rigid body solver. In case viscous/shear force effects are not important in your study (which I believe it is in a microchannel) Immersed solid solver results are acceptable, plus it is faster.

These are just few guidelines. You can find a lot of discussion about this analysis in the forums, as well as the tutorials manual. So do your research first.

I have found better results from fluent in the literature regarding this simulation. It is not as userfriendly as cfx, but I think it is more robust in transient cases with moving mesh.


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