Unable to set large particle generation rate

Yu Wang_21521

The particle generation cannot be set at 400,000 per second, but there will be a drastic reduction in particle number at 0.11s. 

1. Before 0.1s, the particle can generate at a steady rate (400,000).

2. After 0.1s, the particles become discrete, and most particles vanish at the equipment.

I am wondering about the cause and the solutions to this issue. 

Thanks a lot for your great help!!

Stephen Cole

Hi,

 

It looks like the particles are 'exploding' at or after 0.1 s.  From the image this looks like a rotating geometry or screw auger type system.

 

What I would expect is that a particle or particles are becoming trapped between two rotating geometry elements, or a rotating element and a stationary plane.  If the particle becomes trapped the force will increase a lot as the geometry moves through it, leading to high forces and velocities (i.e. particle explosion).

If the particles have artificially been increased in size beyond the actual particle size then it maybe that the original particle would fit through the gap but scaled up material gets trapped.  Or that there would be expectations of breakage where in this case the particles are rigid.  

The other cause of explosions can be time-step related, running at a lower time-step may make the simulation stable.

Regards

Stephen

 

Yu Wang_21521

Stephen Cole_21117 said:

Hi,

 

It looks like the particles are 'exploding' at or after 0.1 s.  From the image this looks like a rotating geometry or screw auger type system.

 

What I would expect is that a particle or particles are becoming trapped between two rotating geometry elements, or a rotating element and a stationary plane.  If the particle becomes trapped the force will increase a lot as the geometry moves through it, leading to high forces and velocities (i.e. particle explosion).

If the particles have artificially been increased in size beyond the actual particle size then it maybe that the original particle would fit through the gap but scaled up material gets trapped.  Or that there would be expectations of breakage where in this case the particles are rigid.  

The other cause of explosions can be time-step related, running at a lower time-step may make the simulation stable.

Regards

Stephen

 

Dear Stephen,

 

Thank you for your kind explanations. 

My previous assumption was that there were too many particles and the volume could not accommodate so many particles, as I saw from the picture that the equipment was full of particles. Is this assumption reasonable or possible under such circumstances? Would this problem be solved by increasing the particle radius and reducing the particle production rate while keeping the constant mass flow rate?

In addition, I am a little bit confused about the particle size being artificially increased beyond the actual particle size. During my simulation, the particle size always remained constant. Will there be artificial changes during the simulation?

 

Thanks again for your great help!!!

 

Best Regards,

Yu

Stephen Cole

Yu Wang_21521 said:

Dear Stephen,

 

Thank you for your kind explanations. 

My previous assumption was that there were too many particles and the volume could not accommodate so many particles, as I saw from the picture that the equipment was full of particles. Is this assumption reasonable or possible under such circumstances? Would this problem be solved by increasing the particle radius and reducing the particle production rate while keeping the constant mass flow rate?

In addition, I am a little bit confused about the particle size being artificially increased beyond the actual particle size. During my simulation, the particle size always remained constant. Will there be artificial changes during the simulation?

 

Thanks again for your great help!!!

 

Best Regards,

Yu

Hi Yu,

With regard to the particle size it is common for the user to increase the size (scale up/coarse graining) to reduce computational time, if you have increased the size of the individual elements in this way it can cause explosions.  

 

The issue is most likely caused by trapped particles causing high forces.