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Old   January 13, 2016, 10:23
Smile Free Surface Modeling
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Abbas Rahimi
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Dear OpenFoamers,

I'm a regular user of OpenFoam but I have a question. I'm interested in free surface modeling to model extrudate shape out of die. I've used PolyFlow for many years and I've done this kinda modeling using Polyflow in the past. I wonder if we can do a similar free surface modeling using OpenFoam. Is there any solver available in OpenFoam for doing so?

Thank you.
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Old   January 13, 2016, 22:26
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I am a beginner in polyflow.
My task is to do free surface modelling by using polyflow. But firstly, i am using differential viscoelastic model for viscoelastic fluid in simple rectangle, After this one, i will move to free surface modelling.
I am facing the difficulty due to evolution parameters. I dont know,how can I can select these evolution parameter?
Can you guide please??
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Old   January 13, 2016, 22:39
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I have tried, but at the end, computation fails and this error comes:
"The evolution scheme can not reach the final value of the evolution
parameter 1. Evolution stops for a value of the evolution parameter
equals to 0.00013801 because the step size has been reduced below the
minimum (as assigned in Polydata)."

And when i decreases the minimum value of delta S, It converges but in CFD Post, the value of velocity are Pressure are zero.

Can you guide me please.
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Old   July 6, 2016, 12:39
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Hi

Have you found out a solution? I have the same problem. Havent figured out yet
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Old   July 7, 2016, 00:25
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what is your step size?
i think your problem is due to step size.
So Reduce the step size.
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Old   July 7, 2016, 16:39
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Is the step size dS min and DS max? Or directly S itself?
I give Sinitial=0, S upper=1, dS initial=0.001, dS min=0.001, dS max=1,
max step no: 200
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Old   July 7, 2016, 16:40
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It says "The evolution scheme can not reach the final value of the evolution
parameter 1. Evolution stops for a value of the evolution parameter
equals to 0.1696 because the step size has been reduced below the
minimum (as assigned in Polydata)."
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Old   July 10, 2016, 19:45
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Step size is dS.
I think your dimensions are in 'mm' that's why minimum step size is required.
If dimensions are small, the problem will reach at steady state earlier.
Use dSmin less than 0.001.
also reduce S, less than 1.
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Old   July 11, 2016, 15:06
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Thanks Arqi it helped , it did not diverge

One more question, unrelated to evolution.
My geometry is cylindirical, however, at the end, the extrudate shape was given as octogonal-like (it has edges)
Is it related to meshing? Any idea? I expect it also as a circle
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Old   July 11, 2016, 23:40
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Sorry, i did not understand your question.
What do u want to ask?
Please elaborate the statement.
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Old   July 21, 2016, 16:47
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I solved the problem now! Thanks!
Now working to learn Polymat
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Old   July 24, 2016, 23:34
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Thats great.
I u need any help regarding polymat then feel free to ask again.
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Old   July 25, 2016, 15:21
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Thanks,

I am trying to use Giesekus model.

Should I use the experimental fit by Polymat? Or can I do it by excel too?

How do you do it mostly?
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Old   July 26, 2016, 01:12
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You have to use experimental fit.
I think we cannot do by excel.
may be you can import the file from excel but i am not sure.
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Old   July 26, 2016, 12:00
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oh ok,
do you have any documents showing how to upload excel file
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Old   July 26, 2016, 22:43
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No, i didn't.
I entered directly in polymat.
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Old   August 2, 2016, 13:34
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Hi again,

Do You know how can I create a 2D polyflow settings?
Should I use my geometry of mesh that I am using for 3D?
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Old   August 3, 2016, 00:09
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first,you have to create 2D geometry in mesh.
then automatically, 2D settings will appear in setup.
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Old   September 16, 2016, 12:49
Default Polyflow- delta P with Giesekus or Cross Model
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Hi,

Does anyone know how delta P scales with zero shear in Cross Model?

Which analytical correlation is being used in Polyflow?

I need to validate my results, but couldnt find any delta P vs Q equation for Cross.

(PS: Even in Giesekus, the program gives a linear relationship between zero shear and delta P. This is strange, right?)
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