Learning Forum

[Nick Fan]

Hello, I am currently conducting a simulation with the following parameters: the injection type is volume, the total mass is 79,789.55 mg, and the total particle count is 40,000. The particles are released using a constant-mass method, with each particle having a mass of 1.9947 mg, and the release occurs in a single instance. I am using a time step of 0.05 for the simulation. The run calculation settings are as follows:

During the simulation, I received the following warning: 

I am unsure how to address this issue and would appreciate any suggestions or advice on resolving it.

[Rob]

What happens if you decrease the time step or increase the max steps in the DPM panel?

[Nick Fan]

Thanks for your reply, Rob. Do you mean that increase the maximum steps in the DPM panel is here?

[Rob]

Yes, but 5000 steps in transient is usually enough. However, with a time step of 0.05s how far would you expect the particles to travel (in terms of cells traversed)? I'd also tend to use High-Res tracking, but that's default in the last few versions so you may want to update the install too. 

[Nick Fan]

Thanks for your reply, Rob!

I am using the Discrete Phase Model (DPM) to simulate the trajectories of PM2.5 particles in an indoor space. For this, I employed volume injection to uniformly distribute 40,000 particles throughout the room, while an air conditioner and air purifier are used to dilute the particles. Additionally, I need the simulation results at 5-minute intervals for analysis. In my previous simulation, where I used 4,000 particles, this issue did not occur. 

Would reducing the time step size be the most appropriate method? If so, do you have any suggestions for the time step size adjustment?

[Rob]

You're looking at parcels and not particles (pedantic point), so how are you releasing the parcels?

[Nick Fan]

Oh, you're right. I used the volume injection type and only released the 40000 parcels initially.