@cgw Can I ask for some assistance regarding a simulation? I am trying to use an STL as a suction pipe to draw in the particles. Is this possible? I’m getting mixed results and none that provide the suction I need.
Here’s my bug report:
Here’s a better bug report:
What do you mean by “mixed results”?
I have got the main component spinning and interacting with particles. I haven’t got any results that create a suction effect due to either mass outflow or negative pressure.
By mixed results, I guess I meant there has been some weird errors etc when trying this method.
No wisdom whether this is even possible with MFix?
There is no way you can mesh your geometry with a 10x10x10 mesh. The grid spacing needs to be smaller than the smallest element you want to mesh (I guess the tube thickness). The bucketwheel cannot be used as a no-slip wall and a moving internal surface. Even if you use it as a moving internal surface, the fluid won’t see it, it is meant to be used for granular flow.
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Thank you for your reply Jeff. I hadn’t considered the mesh size, it was set this low to speed up simulations while I changed the setup, I will adjust this now.
As for the internal moving surface/no-slip wall, is there a way around this? I’m not too concerned if the fluid doesn’t interact with the wheel, as long as the particles interact and the tube creates suction it will produce a result.
If you don’t care about the fluid interacting with the wheel, then the internal surface will be fine. My suggestion is to clean up and simplify the suction tube so it is easier to mesh (remove details that don’t matter and increase the wall thickness so you can use a coarser mesh).
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Much appreciated! Is my mass outflow boundary condition the best method to create negative pressure in the (soon-to-be-simplified) tube?
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It depends on what you know about the boundary. Mass outflow should work, you will need to specify a solids mass flow rate, understanding this will only apply when particles have already moved to the outlet plane.
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I am making slow progress. I have created some partial vacuum, but the pressure drops in the entire boundary box until it reaches a vacuum. I have attempted to add in a pressure inflow, but I get errors regarding the “type of boundary condition”.
Your case runs for me on MFiX 24.3
Are you referring to this warning?
Warning: No Cartesian grid boundary condition specified.
If using cut cells, at least one BC_TYPE must start with CG (for example CG_NSW)
Cartesian grid method (cut cell) will be turned off now.
I believe this warning may safely be ignored.