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Wall Shear Stress Dramatically Increases Everytime I Refine My Mesh |
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April 22, 2019, 07:47 |
Wall Shear Stress Dramatically Increases Everytime I Refine My Mesh
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#1 |
New Member
Jonathan Kartawihardja
Join Date: Apr 2019
Posts: 4
Rep Power: 7 |
Hi there,
I'm currently modelling the fluid flow from a catheter (100% saline) into a vein (100% blood) on Star CCM as part of my thesis project. I've chosen the SST (Menter) K-Omega to model the turbulent regions as the saline interacts with the blood in the vein. I've selected the all y+ wall treatment model and kept my y+~1. I'm currently attempting to do a mesh independence study (GCI to be exact), however every time I increase my mesh by a refinement ratio of 2 (doubling the number of cells), my Max Wall Shear Stress (WSS), Average WSS and Std WSS drastically increases and results in my GCI values to very large for WSS. Also, I believe that my mesh is refined enough as i've gone up to 8,000,000 cells and still my WSS values are still increasing. I've attached a picture of what I'm trying to model and also the WSS plots with each mesh refinement. I'm a complete newbie when it comes to CFD and Star CCM+, so any pointers or words of advice would very much be appreciated (and the fact i don't know who else to ask). Thank you in advance |
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April 22, 2019, 12:57 |
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#2 |
Member
Join Date: Nov 2014
Posts: 92
Rep Power: 12 |
Interesting project, I think you should keep y+ the same and larger than 5 for all mesh size
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April 22, 2019, 13:14 |
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#3 |
New Member
Jonathan Kartawihardja
Join Date: Apr 2019
Posts: 4
Rep Power: 7 |
Hi hokhay, may i ask why y+ should be kept larger than 5 for all mesh sizes?
Thanks. |
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April 22, 2019, 13:25 |
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#4 |
Member
Join Date: Nov 2014
Posts: 92
Rep Power: 12 |
I am an OpenFoam user and the suggested y+ for kOmega SST is between 5 to 30 without special wall treatment. Maybe it is different for Starccm wall treatment. It's better to double check with the user guide
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Tags |
gci, mesh, mesh refinement study, star ccm+, wall shear stress |
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