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particle tracing: particle doesn't move as Re increases

Posted 19 apr 2011, 15:15 GMT-4 Charged Particle Tracing, Computational Fluid Dynamics (CFD), Particle Tracing for Fluid Flow Version 4.1 3 Replies

Sylvana Garcia
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Hi, everyone

I am trying to use particle tracing to explore residence times. As I increased the Reynolds number, (I am working with turbulent flow, kappa-epsilon) the particle just doesn't move. It stays at the inlet boundary. It moved before when I was modeling lower Re. Any ideas on how I can solve this? Is there a better way of studying residence times in fluid flow?

Thanks
Sylvana

3 Replies Last Post 24 mag 2011, 10:05 GMT-4
Sylvana Garcia
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Posted: 1 decade ago 26 apr 2011, 15:28 GMT-4
In case anyone else is having the same problem, Comsol Support pointed out the solution: after the model solves, right click on Study 1 and click on "Update Solution".
In case anyone else is having the same problem, Comsol Support pointed out the solution: after the model solves, right click on Study 1 and click on "Update Solution".
jeremy rutman
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Posted: 1 decade ago 24 mag 2011, 03:59 GMT-4

In case anyone else is having the same problem, Comsol Support pointed out the solution: after the model solves, right click on Study 1 and click on "Update Solution".


How do you get the residence times from the streamline?
I am attempting the same sort of thing.
I have the correct streamlines and now want residence time.
Also if possible, the density of streamlines and/or a set of coordinates for them; it seems the
way to do it is to define a data group, but there is no streamline data group. The
closest is isosurface or isocurve. I could define isocurves for the streamlines but only
in terms of an integral; is this allowed/possible?
TIA
Dr. Rutman
[QUOTE] In case anyone else is having the same problem, Comsol Support pointed out the solution: after the model solves, right click on Study 1 and click on "Update Solution". [/QUOTE] How do you get the residence times from the streamline? I am attempting the same sort of thing. I have the correct streamlines and now want residence time. Also if possible, the density of streamlines and/or a set of coordinates for them; it seems the way to do it is to define a data group, but there is no streamline data group. The closest is isosurface or isocurve. I could define isocurves for the streamlines but only in terms of an integral; is this allowed/possible? TIA Dr. Rutman
Sylvana Garcia
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Posted: 1 decade ago 24 mag 2011, 10:05 GMT-4
Hi, Dr. Rutman

Here is what I know:

When seeting up particle tracing, you can enable the particle trajectories to be shown. Once you have these, you can actually export this data. In version 4.1, right-click on Report and then click on Plot. You obtain a txt file that contains: x coordinate, y coordinate, particle (starting from 0), time, velocity in x, velocity in y. I'm assuming I obtain velocity data because I have the particle tracing on a Velocity Magnitude plot, but I guess you could have any other expression. This exported file, I just post-processed in Matlab to calculate residence times.

About the density, do you mean the density of the fluid along the trajectories? If this is true, then you could either have a numerical value from the file that was exported as described above. So you could plot density and see if the exported data will yield density instead of velocity along the particle trajectories. Or, you could also have a color representation if you right-click on Particle Tracing and then click on Color Expression. Just choose what expression you want to plot and this will add color to the particle trajectories according to the density distribution.

Don't hesitate to write again if you need further clarifying or if you have any other question.

Sylvana
Hi, Dr. Rutman Here is what I know: When seeting up particle tracing, you can enable the particle trajectories to be shown. Once you have these, you can actually export this data. In version 4.1, right-click on Report and then click on Plot. You obtain a txt file that contains: x coordinate, y coordinate, particle (starting from 0), time, velocity in x, velocity in y. I'm assuming I obtain velocity data because I have the particle tracing on a Velocity Magnitude plot, but I guess you could have any other expression. This exported file, I just post-processed in Matlab to calculate residence times. About the density, do you mean the density of the fluid along the trajectories? If this is true, then you could either have a numerical value from the file that was exported as described above. So you could plot density and see if the exported data will yield density instead of velocity along the particle trajectories. Or, you could also have a color representation if you right-click on Particle Tracing and then click on Color Expression. Just choose what expression you want to plot and this will add color to the particle trajectories according to the density distribution. Don't hesitate to write again if you need further clarifying or if you have any other question. Sylvana

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