Few questions about PIC in MFIX-Exa

MFIX-Exa
1

I have few questions on PIC, can someone help me? Thanks

  1. For a binary disperse particles system, how to assign different statistic weight for each of the particles in PIC, since they have large particle size difference?
  2. How to prevent parcels entering the blocked region?
  3. How to extract a mass flow rate in the circular region in the middle of the bed at certain location?
2
  1. You don’t directly assign stat weight in mfix-exa. You assign the parcels_per_cell_at_pack and the stat weight is computed from that which will depend on particle size.
  2. I don’t understand this question, could you elaborate?
  3. If you want to define a region that’s cylindrical that is not currently supported but it may be considered for future development. As is, you would have to make a rect region or, if you really need it to be cyl you could make it out of many regions (stair step).
3
  1. Yes, you are right, Exa uses parcels_per_cell_at_pack. parcels_per_cell_at_pack = (Vc / Vp) * (ep_cp / statwt). My questions is that can we use different values for different sized particles?
  2. Parcels flying out of the computation domain due to high gas velocities or high injecting velocities, is there a way to prevent it?
  3. The geometry is relatively coarse and a stair step is not very precise.
4
  1. no.
  2. a) there is the bc.po_no_par_out = 1 flag which should prevent parcels from exiting a po. TBH, I don’t think I’ve ever used it with PIC though. b) it sounds like there is maybe another issue here, how high are the gas velocities? is it reasonable/expected or a poor solution?
  3. ¯\_(ツ)_/¯

If you would really like to see cylindrical regions (so that you can have cylindrical monitors), please write up a paragraph or so (figure might also help) explaining exactly why the currently available box regions are unsuitable and we’ll present it to @jmusser for consideration as a high-priority development need.

5
  1. It is a riser with high gas flow rate and high solids flowrate. So it is expected.

In the experiment, the cylindrical regions as shown below were used to measure the solids flowrate, to validate our model, a same shape monitor would be very be helpful for this purpose. And since the riser is very long, 21 feet and the CFD cell numbers can’t be refined too much.

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6

Because you are only interested in solids and if this is at a single elevation or few, I might use a region that encompasses all of these 1 - 4 regions of interest and use a solids plot file previously discussed here and do the post-processing on my own.