[Drin]

Hello Guys,


I'm simulating with CFX a accelerated air flow in a pipe and I'm also adding particles at some points at the beginning of the pipe. I'm using the Particle Transport Fluid Model, one-coupled, steady-state and the particles have a inlet velocity of about zero.



My Problem is: When the particles are tracked, they get immediately the velocity of the surrounding gas flow. But this is not physically correct. They can't accelerate that fast. Below you can find a chart where you can see the velocity profile of the particle through the pipe.



The injection of the particle is done with: Point Cone, Cone Angle = 2°C, Particle-Velocity = 0,0001m/s, Particle-Massflow = 8.2*10^-8


Can you help me?

[ghorrocks]

If you need more resolution in the start up acceleration then put a finer mesh there.

The solver is simply saying that given the conditions at the start of injection the particles will accelerate that much in their first integration step. So an alternative approach is to increase the number of integration steps.

[Gert-Jan]

It also depends on the drag relation, particle diameter, etc. What did you specify?