Comparison of First-Order Upwind (DWF) vs. Superbee Scheme for TFM Bubble Simulations

[wuming]

Hi everyone,

I’m currently running Two-Fluid Model (TFM) simulations in MFIX and would like to ask for your insights regarding spatial discretization schemes.

Specifically, I’m curious whether using the first-order upwind scheme (DWF) versus the Superbee high-resolution scheme leads to noticeable differences in predicted bubble characteristics—such as size, shape, and dynamics—in gas–solid fluidized beds.

While it’s generally accepted that second-order (or higher-resolution) schemes like Superbee provide better accuracy by reducing numerical diffusion, I’ve observed that the first-order upwind scheme offers better stability, especially during long-duration simulations.

Unexpected Solid Ejection in MFIX-TFM Simulation of Bubbling Fluidized Bed Post-Steady State

Hi, everyone, I’ve encountered an intriguing issue while simulating a bubbling fluidized bed using MFIX-TFM. After achieving steady-state fluidization, at a certain moment, the solid phase is abruptly blown out of the bed by what seems to be a strong virtual airflow. This results in a noticeable decrease in the volume of solids within the bed. Initially, I suspected that this was due to too large a time step (adaptive steps ranging from 1e-3 to 1e-9), so I adjusted the range to 1e-4 to 1e-9. Un…

Has anyone compared these two schemes in similar contexts? If so, did you notice significant differences in bubble behavior? And how do you typically balance accuracy versus stability when choosing a discretization scheme for TFM?

Thanks in advance for your advice!

Best regards,

[gq05021]

Hi Wuming,

We did have tried to study the effect of spatial discretization scheme on the prediction of bubble behavior in our past study ( A two fluid modeling study of bubble collapse due to bubble interaction in a fluidized bed - ScienceDirect ). We cited the work of The effect of numerical diffusion on simulation of isolated bubbles in a gas–solid fluidized bed - ScienceDirect, where you can find more detailed comparsion.

Hope this helps.

[kjetilbmoe]

650122.pdf