# Particle Tracking

Member

Hi,

I have a simple axisymmetric 2D model. Uniform flow at the inlet (air) and pressure outlet. In the DPM model: Injection type is surface, particle inert, diameter uniform with zero velocity as they should move by the air movement, and the default total flow rate 1e-20 kg/s.

The problem is the number of particles trapped decreases when I increase the air velocity. Should they increase as velocity increases from the momentum equation?

So if the velocity is 0.001 m/s I get 7 particles trapped while if the velocity is 0.01 m/s, I just get 2. The particles are water-liquid. There is only one side of a wall trap as you can see in the image. Steady state simulation with no heat transfer involved.

Thanks,

• Forum Coordinator
edited October 2018

Hi,

Is your flow solution converged? Can you please run only flow and once it is converged, please see velocity vectors and other contours at the location.

Regards,

Keyur

• Member
edited October 2018

Hi,

Yes, it does converge and I looked at velocity contour and vectors. The problem is, the particles once they are close to the plate in the middle, they fly around it. Why most of them fly around the plate and don't hit it?

Thanks,

edited October 2018

Hello,

What is the particle diameter range like?

Could you please share screenshots of the vector plots of your flow for better clarity? Please also share a screenshots of your particle tracks.

Thank you.

Best Regards,

Karthik

• Member
edited October 2018

HI,

Can you check the do you get any recirculation close to the wall. I guess the recirculation bubble will affect the flow and trapped particles. You can check the recirculation bubbles for both the velocities. It gives you more information on particle trapped. You can plot the streamlines and check.

Regards,

Seeta

• Member
edited October 2018

Hi Kremella and Seeta,

Thank you so much for your help. There are some circulations under the plate, which is an area I am not interested in. Could this affect the flow above the plate? it is axisymmetry. Here are vector plots, streamlines, and particle tracking contour:

closer to the plate:

finally the particle tracking:

Thank you,

edited October 2018

Hello,

Could you please share a screenshot of your mesh density in the step region? I hope you have sufficient resolution near the step. Have you performed any grid independence studies on this problem?

Thank you.

Best Regards,

Karthik

• Member
edited November 2018

Hi,

If you could see the last picture which is closer look of particle tracks, we can easily tell that how many particles are trapped. I could see only two particle traces which hit the wall and trapped, rest of the traces are just flowing along the plate.

As Karthik mentioned, one thing would be the mesh. I hope you would have the good mesh near the plate. Can you refine the mesh near the plate and check how many particles are trapped. I could not see any recirculation near the plate so number of particles trapped are less. Check the recirculation zone with low velocity case as well.

Regards,

Seeta