Seek help! confusing bianry fluidization simulation

MFiX How to
#1

Hi, Everybody

It is very confusing that binary particle mixture can not be fluidized while each component can be fluidized, as shown in following three figures. Bed in the third case was being a dead bed. Expect for particles simulated, all settings of these cases are the same. For the binary fluidization simulation, its simulation time is much much longer than that of other two cases. It took about eight hours to run 0.03s simulation. I don’t understand what is the difference on the numerical calculation for binary fluidization.
I sincerely hope someone can help me and give me some advice. :pray:

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image1280×267 69.5 KB

fluid_dem_2d_small.zip (12.8 KB)

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image1280×294 69 KB

fluid_dem_2d_large.zip (12.3 KB)

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image1211×403 125 KB

fluid_dem_2d_binary.zip (19.1 KB)

#2

Running a polydisperse DEM case in 2D is not well defined. Try to set up a 3D simulation with a width (z-direction) slightly larger than the large particle size, and use one cell (kmax=1) in the z-direction. The case with binary system will take longer to run because a) the smallest particle drives the time step down and b) the des grid needs to be larger to accommodate the large particle and thus will loop through more neighbor particles than the case with only small particles.