I simulate the gasifier with a diameter of 0.5 m and a length of 5 m. what should be the grid size. I work in 2D. The particle diameter is 0.5 mm and the mesh is 20 X 200. I get the error dt <dt_min continuously. dt_max is at the level of 10 ^ -5. I’m getting smaller, but the error continues. First,…

[image] myazgi: dt <dt_min means that the simulation is not converging. [image] myazgi: sum of solid phase mass fractions gives an error not equal to 1 probably means that something is wrong with your chemical reactions. Make sure they are balanced, conserve mass, etc…

I have done this work without any problem in a 0.05 m diameter and 0.5 m long gasifier. However, when I did scale up, it started to give these errors. There is no problem in chemical reactions. Increasing the number of mesh or decreasing the dtmax value does not solve the problem. What else could be…

How much is your maximum iterations in numerics tab? maybe you can increase this value because of convergence problem. Sometimes the number of iterations may not be enough. Secondly you can disable “Detect stall” and maybe “Enable max wall time” at Run tab. Because mfix tries to converge by changin…

It’s all done. The problem still continues. I did not know that I would encounter such a problem when I scale up. I had no problems on a lab scale. This problem occurred when I enlarged the gasifier and capacity. Lowering dtmax or increasing mesh is not the solution. It gives error in 0.5 seconds of…

Could you share you case files? Did you run in a debug mode to check your code?

Few things needs to be considered, For 2D simulation, make sure all the parameters scaled correctly, especially the boundary conditions. Since it is the biomass gasification simulation with TFM, so the momentum equation for all 3 phases, also the species equation for gas and biomass should be set …

Hi, Musa, I’ve come across the same issue that you mentioned. I’m curious to know whether your problem has been resolved. If so, I’d really appreciate it if you could share the solution. Thank you in advance for your help! Best regards,

See reply at [image] Warning: The sum of mass fractions is not equal to one MFiX This approach is implemented in MFiX 25.1, see MFiX 25.1 Release Announcement - NETL Multiphase Flow Science

Dt<dt_min and sum of solid phase mass fraction is not equel one error

MFiX

cgw May 5, 2025, 12:35pm 10

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