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Old   June 12, 2020, 07:12
Default Not showing stream lines
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Hi everyone

I have a problem which happens to me rather often.

After running simulations (usually not very complicated ones, in report section when I use "Stream Line" for velocity, my stream lines start at inlet but in the way to the end they become less and less and finally I will not have any streamline representations.

Does it mean my results are not accurate? (my simulations usually converge up to 10^-4)
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Old   June 14, 2020, 12:47
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Quote:
Originally Posted by shahin1 View Post
Hi everyone

I have a problem which happens to me rather often.

After running simulations (usually not very complicated ones, in report section when I use "Stream Line" for velocity, my stream lines start at inlet but in the way to the end they become less and less and finally I will not have any streamline representations.

Does it mean my results are not accurate? (my simulations usually converge up to 10^-4)
Hi Shahin,


I don't know properly why does it happen, but in CFD post the option to plot streamlines always worked properly for me. Have a try and share your answer to know if it worked for you.

Regards.
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Old   June 15, 2020, 08:08
Default Streamlines
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Quote:
Originally Posted by shahin1 View Post
Hi everyone

I have a problem which happens to me rather often.

After running simulations (usually not very complicated ones, in report section when I use "Stream Line" for velocity, my stream lines start at inlet but in the way to the end they become less and less and finally I will not have any streamline representations.

Does it mean my results are not accurate? (my simulations usually converge up to 10^-4)
By less and less do you mean in time or in space? In other words, as the simulation progresses, none of the streamlines appear or the streamlines start from the inlet and stop somewhere in the middle of the domain. If it is latter, then just increase the number of steps from 500 to 10000 or higher.
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Old   June 16, 2020, 10:18
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Yes, they become less and less as we move from inlet to outlet, it means that streamlines stops where between inlet and outlet.

Can you please tell me what do you mean by increasing the steps? are you referring to number of iterations (if that is so I have already increased the number of iterations and it did not work)
I was suspecting that maybe the residuals are too large and my model is not converged! (my residuals are in order of 10^-4 for continuity and 10^-5 for velocities.

The simulation is about the flow of CO2 inside a serpentine channel (should be supper easy!)
Here are some pictures from my results, if they help!
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Old   June 16, 2020, 10:21
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Iterations are for continuous flow. You need to increase steps, shown on the Pathlines panel. Default would be 500.
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Old   June 16, 2020, 11:17
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well in the version I am working with, for controlling the streamlines there is an option named "max point" by which I can increase the number of streamlines. Is it the same as steps you are referring to? if not can you address me a bit more accurately where this pathlines panel and step are? (they are in results right?)
By increasing this number from 25 to 1000 it helped extending the streamlines a bit but as you can see there are too many of them and the problem is not still solved.
Also, do you believe this could be due to a bad convergence and wrong results or you think it just a problem in representation?
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Old   June 16, 2020, 11:33
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You are not using Fluent, but CFDPost. The control in CFDPost is not straightforward, I suppose under Limits (or Symbols) tab.
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Old   June 16, 2020, 12:01
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Thanks mate

I used Fluent and the problem is solved and all the stream lines are contentious,
just wondering why it happens in CFD post, the tabs you referred to are just for customizing and do not actually increase the length of the steam lines.

It helped me a lot already
Thanks
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Old   June 16, 2020, 12:11
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In CFDPost, increase the Max Time under Limits tab.
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