Issue of uneven gas-solid flow in case studies

MFiX
1

The initial and boundary conditions in my example are completely symmetrical. However, during the calculation, there was uneven gas-solid flow, as shown in the figure, which caused a deviation in the results of gas diffusion and easily formed a flow dead zone, which is difficult to recover in subsequent calculations. I would like to ask everyone about the reasons for this situation? My guess: There are issues with the time step and grid settings.

P1
P1878×623 101 KB

backflow-adjust_2025-12-14T184924.658263.zip (137.3 MB)

2

I ran in DMP and I do not see that dead zone:

image
image713×662 54.3 KB

The grid spacing has large jumps in x and y direction:

image
image649×542 98.7 KB

You should try to use a smooth transition instead.