[Andri Surya]

I have a problem here, i try to simulate flow pneumatic grain conveyor/pneumatic transport.. on the vertical pipe 3D. I use fluent software, this are some parameters that I use :
1. the steady condition
2. gravity enabled
3. multiphase eulerian Dense DPM (phase 1=air and phase 2=wheat 2mm)
4. viscous k-epsilon (i dunno what i must use standard/RNG/reliazible)
5. drag law on the discrete phase is gas-solid (wen yu/gidaspow/syamlal o brien)
6. Diameter of the pipe is 10 inch
7. total flowrate discrete phase is 37.8 kg/s (wheat density is 900 m3/kg)
8. phase 2 is set as granule (cmiiw because the diameter of the wheat is 3mm, and its length is 5mm, is it still granule?)
9. velocity inlet for the air is 32 m/s
10. pressure outlet is -25000 Pa
11. the length of the vertical pipe is about 20 m

When I set all the parameters and i try to calculate.. On the iteration 15 to 20 always report as divergence, and its report "increase relaxation sweep" and "decrease coarsening group"... what it means? what should i do? is that my parameter correct to do this simulation (pneumatic transport)?
Thank you for your patience brother