Asymmetry in cross-sectional profiles

MFiX
#1

Hi,

I am using MFiX 22.3.1 for horizontal flow models with 3D TFM (Cartesian cut-cell coordinates).

I find an asymmetry in the solids-gas interface in the cross-sectional profiles for all the cases, with the left side depressed; I have tried different grid resolutions and the profiles are similar, as you would see in the attached visualisations using VisIt. The visualisations are for a pseudo-3D ‘disk’ model, with a single layer of axial cells with axially periodic BC (.mfx attached), however, the profiles are similar for long pipe models with Mass Inlet - Pressure Outlet BCs too. I have run these cases for sufficinetly long process times (up to 30 s) and these profiles are largely time invariant. I use the default tolerances for the Mesher, other than the dot product tolerance at 1E-5 and the snap tolerances at 0.09. I have used a cylinder resolution of 170 under the ‘Geometry parameters’ for the cases.

Am I missing something?

Thank you.

hdk067L.mfx (10.5 KB)

X-S-Asymmetry
X-S-Asymmetry1725×799 208 KB

#2

Hi,

I could get a symmetric profile and the inherent fluctuations of gas-solids flow by specifying No-Slip Wall BCs (with no applied granular temperature flux); visualisation attached.

The earlier runs that produced asymmetric profiles and apparant steady state flow were due to Free-Slip Wall BCs (widely recommended in the litreature).

Thank you.

HDK067_NSW
HDK067_NSW1067×640 26.4 KB