Animating particles without adding more over time

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cfb
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Animating particles without adding more over time

Postby cfb » Mon Jan 03, 2011 9:07 pm

I've got a simple 2D Cartesian incompressible flow solver written for a project which is now solving unsteady flows, and I've been looking for a while but haven't found anything on my question:

What's the easiest way to animate particles in an unsteady flow?

In particular, how can I seed a bunch of massless particles at the first time step (in a regular grid, say), and let them evolve according to the flow WITHOUT adding more particles? (This is because it's for a lid-driven cavity, where it doesn't make sense to add more particles with time.)

(By the way, I'm using Tecplot 360 2009, on a Windows machine sometimes and a Mac other times.)

By just looking at the options, I found Calculate Particle Paths and Streaklines under Analyze, which seemed perfect for this. I was disappointed to find that after calculating a particle path, it always either displayed the whole thing or none of it. If I'm missing on an easy way to just display where the particle is at a current time step, please let me know.

The other option was streaklines, and with this I had more success, since at least with streak lines, they do evolve in time and show a good sense of the instantaneous motion. In fact, I got quite close to what I was looking for by using the Scatter layer and just reducing the size to 0.5% so that you see individual particles swirling around.

But there's still the issue of particles being added continuously. For a flow with inflow and outflow, adding particles is great, but for a closed cavity, I want a fixed number of particles. You can modify the Release value in Calculate Particle Paths and Streaklines down to ~1.17e-38 (not sure why 0 isn't allowed...), which effectively means that after the first particle is released from each starting position, no more will be added.

So now I'm very close, since the number of particles is fixed. But in every possible way of viewing these streaklines of 1 particle (Scatter, Vector, etc.), the initial particle positions always stays fixed and visible in addition to the moving particles. I clicked all over in the Zone Style options turning off Scat Show or Vect Show for various zones of the streaklines, but I just could not get that initial position to disappear! Anyone have any ideas here? It's a minor thing, but it's definitely distracting to see stationary particles in the unsteady flow.

Maybe I shouldn't be using streaklines for this, but it does seem very close to what I want.

If you're curious as to what it looks like currently, I uploaded a video at
<a href="http://cfb.qqnoobs.com/apcflowsolver/LidRe10000.avi">http://cfb.qqnoobs.com/apcflowsolver/LidRe10000.avi</a>

Any help is appreciated, thanks!

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