Hi all,
I’m working on a simple case of invert trap with particles inside.
The case is uploaded here.
I have a new problem with this case.
I want to simulate the trap flow with water. The particles are initialized with external particle_input file.
The fluid density is 1000kg/m3.
When I run it, it will stop very soon and gives the error message that dt<dt_min.
I tried to decrease the time step down to 1e-9 s, but still got the same error.
trap_2019-04-30T121558.zip (754.5 KB)
However, when I remove the trap, which becomes a simple duct flow, it can run successfully.
I guess there is something wrong with the geometry setup.
The trap geometry is generated within the MFIX using STL files.
I couldn’t find what is wrong with this setup.
Can someone help, please?
Thanks!
You only have one grid cell spanning the length of trap. This is not nearly enough to resolve the flow in the channel, let alone capture the effects the trap would have on the flow. Increasing the number of cells in the x direction might fix the convergnce issues, but I didn’t test this solution.
I would not use an STL given the simple geometry. Instead, use blocked walls to remove the section of the domain you don’t want fluid. Attached is a case that runs but has more grid cells in x and uses block walls to define the trap.
trap.mfx (11.1 KB)
Thank you very much!
It did work now.
But I don’t really understand why it does not work well with STL geometry.
Does it mean that it’s always better not to use STL for simple geometry.
The problem was not the STL, it was your mesh in the principal flow direction. You only had ONE cell defined over your trap.
As far as the STL, I think Dr. Musser was indicating that a simple geometry involving walls is always better than managing an STL file.
Alright. I see.
I only focused on the main channel and forgot to resolve the trap.
Thank you all for helping a beginner on MFIX!
