[Billy_]

Hi,

Is there any alternative boundary conditions which allow say, a box to be filled by particles. What I mean is that the particles are injected from the inlet and once injected, the 'outlet', instead of letting the particles escape or reflect, will stop the particles from escaping and will fill the box. I have played around with all boundary conditions but none work. 'Trap' just lets the particles disappear, and 'reflect' lets the particles bounce off and they never come to rest? Should the particles come to rest eventually if only falling from gravity, so far I have not been able to gain this result, which is obviously showing unrealistic results.

Alternatively, I have tried using patch in the initialization tab to patch in the solid particles however as I am only using the DPM and laminar model I cant do this either. I'm only using these models as gravity is the only real force in play if particles are being dropped from a height with no significant air flow.

So my questions:

1. Are there any boundary conditions that will allow me to fill a box with solid particles?
2. For particles falling from an inlet with no significant air flow, are the DPM model and laminar flow correct for this situation?
3. Can the patch initialization tool 'patch' solid particles into a volume at t=0? Basically my end goal is to analyse flow from a tank/silo but with solid particles instead of water.

Thanks in advance.

[DnyanMiri]

I hope you have found a solution to the above problem, if not I would like to suggest some points
1. Why don't you give 'wall' with 'Reflect' BC instead of 'outlet'. I think this will serve your purpose.
2. You have to check the volume fraction of the components. DPM is recommended of fractions below 12. You can use DDPM for a denser domain.
3. I'm not sure about this, as I have not used DPM with solid particles. I used it for droplet evaporation where I was able to assign an initial fraction of water vapor present in the domain. Hopefully, you can also do it for solid particles.
Thanks

[vinerm]

Ideally, suspended particles can be simulated using DPM; suspended implies suspended in the fluid or collected as a heap. However, the practical challenge is that the position requires continuous update. If position change is insignificant, time-step required would be very small.

Another aspect is if the only force being considered is gravity; and to do that you need to ensure that drag coefficient is 0 and that would require drag function modification, default is spherical; then the particles will fall on to each other. This requires a model that can predict particle-particle interaction.

So, the only solution is to use DPM.

Do note that the Initialization panel can only initialize Eulerian fields. Lagrangian vectors are initialized using injections. To patch whole zone with particles, use either a volume injection or File injection. Volume injection is a beta option.