pressure drop , restart run, upper limit of temperature and fluidization of lowest layer of particles

hello cfdemers,

some questions arise when I use the cfdem, hope you can give me some suggestions.

#question on pressure drop
As we know, change of pressure drop with inlet velocity is used to test the minimum fluidized velocity when justify whether the simulation is correct.
So I take a test using probe and pressureDrop function in controldict.
the simulation parameters are:
volume:60mm*60mm*600, x y z
grid:8*8*60, x y z
particle diameter:4mm
particle number:15660
particle density:2700kg/m^3
minimum fluidized velocity:1.77m/s

and two probe locations are used:
(0.03 0.03 0)
(0.03 0.03 0.5)

gradually increase the inlet velocity from 0 to 2m/s, and then take two plots:
one is:
pressure drop of two probe location versus inlet velocity,
the other is:
pressure drop of inlet and outlet versus inlet velocity(using pressureDrop function in controldict)

But the pressure drop didn't increase with the inlet velocity gradually, instead it oscilated with large amplitude when the velocity goes from 0 to 1.7m/s.

so i suspect whether the probe locations is not suitable for this calculation or not. or it is he problem of the setting of the calculation. such as the grid is fine or other........
and the pressure drop of inlet and outlet patches with velocity is more stranger....

so could someone give some suggestions on how to test of minimum fluidized velocity.

#question on the largest temperature the cfdemSolverPisoScalar
I want to know the upper limit of temperature in the cfdemSolverPisoScalar solver.
it is sure that the temperature should not overpass 600'C because the radiation is not considered in the solver.
when dig into the code, it seems that the value of DT and viscosity is constant in the simulation process.
dose it have little effect on the simulation result when the temperature increase with a large value?

#question on the lowerst layer of particles
several cases have been tested with different kinds of particle(Geldart A,B,D) and different geometry.
A common problem is particles in the lowest grid cann't be fluidized if the inlet velocity is a little larger than the mimimum fluidized velocity.
the method I take is using a fine grid for the lowest layer. always the grid size is similar to the particle diameter.
but I don't know whether it's the better way or not.

#BTW, another question on the restart of cfdem
I have noticed that a liggghts.restart file lies in the Folder CFD/..., so if I want to restart the simulation with a longer time, what I need to do is just set the item "startFrom" as "latestTime" in CFD/system/controldict?

thanks for your hints.
S.L