Hello!

I have modelled the unsteady injection of water into a straight pipe with turbulent air flow (standard k-e model with standard wall functions). I use the Discrete Phase Model to model the drops (cone injection). I can see from contour plots that the mass fraction of H2O actually increases along the pipe with each timestep as the water is injected and evaporated, as well as decreases as the gas flow transports it towards the outlet. So far, so good.

However, when I want to view the Particle Tracks, the plot is all black. The Min and Max value-fields show realistic values whichever Particle Variable is plotted, as does the colour scale to the left in the graphics window, but the view itself is all black...

I mark all injections under "Release from Injections", I have also tried to make an XY plot instead but it's the same (all black), I have drawn the grid to see that the pipe is zoomed up nicely and removed it thereafter to try to see the coloured particle tracks, but nothing helps...

What could be the cause for this?? Any ideas or help is greatly appreciated!

Thanks, Henrik

Hi

Using unsteady dpm injection, i guess "flow time" exceeded the "injection time duration" . check in injection menu if the start and stop injection time are well set, and compare them to the actual flow time . Hop it helps

Mohamed

Thanks for the answer!

Yes, you are right! The injection lasts for 12 milliseconds and I have run the simulation much longer (53 ms, to follow the particles as they proceed through the domain). Do you mean that it is not possible to view particle tracks if injection time > flow time in FLUENT? Is there some way to get around this? I was planning to inject for 12 ms with 238 ms between injections (that is, 4 injections per second), and it seems viewing particle tracks is a great help to see what happens.

Once again thanks, Henrik

Hi again!

I tried to run the simulation for 10 ms only (duration of injection is 12 ms), with timesteps of 1 ms. However, I still cannot see the particle tracks... I have a feeling that I maybe misinterpreted what you meant by "flow time"? Anyone who has a guess what might be the problem?

Thanks, Henrik

Hi HEnrik No u didn t misunderstand what i mean to say. In this case try to reduce the length scale under "tracking parameters" in dpm model definition (define models dpm tracking ...) U can also make only one time step iteration and check if the droplet injection is well set up!

good luck Mohamed

check that the particle track style options is changed from "line" to "points"- i had similar problem. see if that works

It's seems this was actually the problem this time! After changing to points, I can now see what I want.

Big thank you's to you both for taking the time to help me solve this!

/Henrik