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August 4, 2015, 12:23 |
A Problem with my OpenFoam animation
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#1 |
Member
Mike
Join Date: Apr 2011
Location: Canada
Posts: 83
Rep Power: 15 |
Hi there,
I am new to OpenFoam and just started working with that. I have conducted a test on a 2D cylinder at Re=100 (laminar), just to make sure that the basics of my openfoam simulation are OK. The simulation went well and I also made an animation for the flow evolution which can be downloaded from here: https://www.dropbox.com/s/zqnvxg7hbt...-SLOW.avi?dl=0 There is some thing that puzzles me a bit. Although it is quite obvious from the contour structures and topology that the flow is from left to right, in the animation it seems that those high U contours are begin convected from the outflow boundary to the cylinder. It is not a visual mistake as I refined the time step and got the same result. I suspect there might be some more subtleties related to OpenFoam. I checked whatever I knew but could not find the problem. If I ran the animation in the reverse order then it looks quite nice! I'd appreciate your help. Last edited by saeedi; August 4, 2015 at 14:06. |
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August 4, 2015, 13:55 |
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#2 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,775
Rep Power: 71 |
Quote:
Are you sure that you have the correct order of the zones in Tecplot? It seems simply reversed ... |
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August 4, 2015, 14:04 |
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#3 |
Member
Mike
Join Date: Apr 2011
Location: Canada
Posts: 83
Rep Power: 15 |
Yes,
I checked it. It seems that the timestrands are correct and in the right order. |
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August 4, 2015, 14:07 |
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#4 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,775
Rep Power: 71 |
try to do the animation with a vector plot, it could be more useful
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August 4, 2015, 14:10 |
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#5 |
Member
Mike
Join Date: Apr 2011
Location: Canada
Posts: 83
Rep Power: 15 |
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August 4, 2015, 14:15 |
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#6 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,775
Rep Power: 71 |
Quote:
it still seems the order of the zones is reversed.... |
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August 4, 2015, 14:20 |
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#7 |
Member
Mike
Join Date: Apr 2011
Location: Canada
Posts: 83
Rep Power: 15 |
But if you look at the flow development, from time=0 to the first couple of snapshots, it shows that the flow is developing correctly and I think that is an indication that the zone order is right. But suddenly we see that reverse behaviour around time=1.
Also, when I do it in tecplot frame by frame, the time associated with each snapshot and their orders are OK. It is really strange. |
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August 5, 2015, 13:15 |
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#8 |
Member
Mike
Join Date: Apr 2011
Location: Canada
Posts: 83
Rep Power: 15 |
No more idea?
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August 5, 2015, 13:22 |
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#9 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,775
Rep Power: 71 |
Quote:
I suspect that we are victim of some optical joke due to the movie... I tried to see each frame of your movie and it seems to work fine |
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August 5, 2015, 13:24 |
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#10 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,775
Rep Power: 71 |
you know, depending on the sampling frequency we can have a sort of stroboscopic effect....
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August 5, 2015, 13:27 |
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#11 |
Member
Mike
Join Date: Apr 2011
Location: Canada
Posts: 83
Rep Power: 15 |
That came to my mind as well.
But when I refined the time-step and consequently the writing interval by 4 times, I still observed the same thing. |
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August 5, 2015, 13:44 |
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#12 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,775
Rep Power: 71 |
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August 5, 2015, 13:46 |
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#13 |
Member
Mike
Join Date: Apr 2011
Location: Canada
Posts: 83
Rep Power: 15 |
Yes I did.
Same thing. That's Why I always prefer to use my own code. It is way easier to track. |
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