Free Surface Modeling

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 January 13, 2016, 09:23 Free Surface Modeling #1 New Member   Abbas Rahimi Join Date: Jan 2013 Posts: 28 Rep Power: 13 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.

 January 13, 2016, 21:26 #2 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 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??

 January 13, 2016, 21:39 #3 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 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.

 July 6, 2016, 11:39 #4 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 Hi Have you found out a solution? I have the same problem. Havent figured out yet

 July 6, 2016, 23:25 #5 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 what is your step size? i think your problem is due to step size. So Reduce the step size.

 July 7, 2016, 15:39 #6 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 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

 July 7, 2016, 15:40 #7 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 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)."

 July 10, 2016, 18:45 #8 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 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.

 July 11, 2016, 14:06 #9 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 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

 July 11, 2016, 22:40 #10 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 Sorry, i did not understand your question. What do u want to ask? Please elaborate the statement.

 July 21, 2016, 15:47 #11 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 I solved the problem now! Thanks! Now working to learn Polymat

 July 24, 2016, 22:34 #12 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 Thats great. I u need any help regarding polymat then feel free to ask again.

 July 25, 2016, 14:21 #13 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 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?

 July 26, 2016, 00:12 #14 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 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.

 July 26, 2016, 11:00 #15 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 oh ok, do you have any documents showing how to upload excel file

 July 26, 2016, 21:43 #16 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 No, i didn't. I entered directly in polymat.

 August 2, 2016, 12:34 #17 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 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?

 August 2, 2016, 23:09 #18 New Member   wasisaleem Join Date: Nov 2015 Posts: 17 Rep Power: 10 first,you have to create 2D geometry in mesh. then automatically, 2D settings will appear in setup.

 September 16, 2016, 11:49 Polyflow- delta P with Giesekus or Cross Model #19 New Member   oz oz Join Date: Jan 2016 Posts: 9 Rep Power: 10 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?)

 Tags extrusion, free surface flow, multiphase flow