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Transient particle path for twin screw extruder

Posted: Sat Oct 15, 2011 9:58 am
by raghumohan
I am trying to get particle path in a twin screw extruder (for one screw rotation). I have 36 data files having position and velocities (in x,y,z-directions). Each file consists data of nodes for every 10 degree rotation of screw. I have loaded all files and gave the constant delta value (animation time step) as .0277 in "Edit time strands dialog". Then I have plotted the stream line in forward direction giving a starting point (node position which is at the entrance of extruder and lies between the screws and barrel). A streamline has been created and then I have defined the analyzer field variables as velocity variables (in x,y,z directions). Then I calculated the paticle path giving the intigration time as 1e-6. But the particle path created is very small(too small) and it goes back to the entrance of extruder after travelling for a while (path nearly similar to a semi circle). [ I have followed the webinar "Calculating Particle Paths and Streaklines"
for this]

Then I loaded only 6 files of data and checked the particle path again, but it gives the same particle path (also same streamline) again.

I removed the time step animation (removed constant delta value) and then plotted streamline which was much longer than the former one. I also calculated the particle path for this situation, the particle path was also long enough and moving forward.

Please suggest me some way to get this particle path with time step animation. Also please let me know if you have any questions on the data I gave here.

Re: Transient particle path for twin screw extruder

Posted: Mon Oct 17, 2011 1:23 pm
by Chris Idso
Hello Raghu,

When calculating particle paths one must remember to set the Itegration Time Step in the Analyze/Calaculate Particle Paths/Streaklines dialog to be appropriate for your data.

1e-6 was appropriate for the data used in the example you followed, but it is not appropriate for your data. Please rerun the calculation using 0.0277 for the integration time step, and see if that improves the results.

Re: Transient particle path for twin screw extruder

Posted: Tue Oct 18, 2011 11:06 am
by raghumohan
when I used the intigration time step as .0277 the particle path formed looks like a curve having sharp turns(edges). But when I used the value 1e-6 a smooth curve is formed. Also, These both curves are following almost the same path. Among both of them which one should I consider the correct particle path?

Re: Transient particle path for twin screw extruder

Posted: Wed Oct 19, 2011 5:54 am
by salter
They are both correct for the stepsize you used. Try decreasing the step size, but not excessively. You may also want to increase the maximum number of steps.