I’ve recently done a quick, qualitative comparison between DEM and PIC results for a simple, pseudo-2D fluidized bed using MFiX version 23.3.1. I’ve attached videos of the behavior of both systems.
As you can see, the difference in behavior is apparent. Compared to DEM, the bed of the PIC simulation is less fluidized and exhibits hindered bubble formation.
I fully understand that there will meaningful differences in how the two models behave, but I did not expect it to this degree, which makes me think there’s something wrong with my project setup for the PIC case. I’ve compared my setup of the .mfx file with some of MFiX’s PIC tutorial files and haven’t found any difference in setup that would cause erroneous behavior. I’ve attached the .mfx file for the PIC simulation in case that would be helpful to the support team (ignore the filename, it’s outdated). If this is expected behavior, please let me know. If not, please let me know what I should do to better set up my PIC simulation.
I checked the .mfx file you provided and found that psfac_fric_pic = 100.0 in the PIC model parameter settings is a bit large, maybe you could try a range of 10-40.
Hi. Thanks for taking a look and giving me that suggestion. I used that value for the constant because it is the default value used by MFiX and is the referred to as the “typical value” for this term in the 1997 paper from Snider/O’Rourke on MP-PIC.
I think your suggestion could definitely help with this behavior though, so I’ll give it a shot and see if it makes it better. Thanks again!
There is no paper. This is just simple, turbulent fluidized bed with Class D particles I set up to do some qualitative comparisons between the two solvers.
Hello black233,
My case have the same problem. Although I set the parameters in IC and BC pages as accurately as possible, the simuation results obtained form MFIX-PIC still has a huge difference between the experimental situation. I mean, the PIC can not exhibit a good fluidization phenomenon.
I also compared the pressure difference of the bed material at different heights, which can have a good agreement with the experimental value.
Have you solved this problem? Or do you have any suggestions?
Hi. I forgot to post an update, but I took the advice of someone further up the thread and adjusted the pressure constant in MP-PIC’s empirical stress model down to I believe 10 Pa. I experienced slightly better fluidization under these conditions, but it still undershot the bubble size and formation rate of DEM by a significant margin.
As far as suggestions go, I don’t have any in this case. I’ve worked pretty extensively with PIC methods in the past through commerical software and never had to adjust the Ps constant to get realistic fluidization. So I’m not sure what further parameters could be tuned in this case. If you come across anything yourself, please let me know