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1-Way FSI CFX to Mechanical - Imported loads (pressure/forces) not matching? |
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August 16, 2018, 16:36 |
1-Way FSI CFX to Mechanical - Imported loads (pressure/forces) not matching?
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#1 |
New Member
Moustafa El-sawy
Join Date: Aug 2018
Posts: 4
Rep Power: 8 |
Hi everyone, I am trying a very simple example of flow going through a 90 degree bend pipe. After my CFX sim, which I verify the results with hand calcs for a simple 90 degree bend pipe flow, I import the load (pressure) to a static mechanical analysis and expect to get the same forces I get from CFD?
However, when I look at the imported loads summary I find that they dont match. Is this due to a meshing issue or how does ANSYS Map the pressures from CFD to nodal forces in static mechanical? Does my solid (pipe) mesh has to match exactly the fluid (water inside pipe) mesh at the interface between them? It shows 100% of forces are mapped but they still dont match (not within 5% of each other) Here is what the imported load summary shows: https://imgur.com/a/biVualR My current mesh in ANSYS Mechanical is alot more finer which is recommend by looking at the documentation provided by ANSYS (take a look here at the bottom of the page): https://www.sharcnet.ca/Software/Ans...teraction.html Your feedback is appreciated. |
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August 16, 2018, 21:31 |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,841
Rep Power: 144 |
FSI can handle non-matching meshes.
Does the force balance improve when you refine the mesh?
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Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum. |
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August 16, 2018, 21:43 |
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#3 |
New Member
Moustafa El-sawy
Join Date: Aug 2018
Posts: 4
Rep Power: 8 |
I did not try several meshes, but I did notice the results do vary greatly when the mesh is different. I was hoping someone had experience with this issue. Maybe ai can try several runs tomorrow with different meshes (although I am still fairly new to usinf ANSYS workbench) and post here to help anyone with a similar issue.
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August 16, 2018, 21:51 |
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#4 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,841
Rep Power: 144 |
If your results are changing between meshes that is a big sign your mesh is not fine enough. There is no point looking at other issues until you have a mesh fine enough to be accurate.
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Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum. |
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August 16, 2018, 21:54 |
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#5 |
New Member
Moustafa El-sawy
Join Date: Aug 2018
Posts: 4
Rep Power: 8 |
My CFD results are converged and dont change with changing ghe mesh. I am talking about the import load step, thats what changes and even with a super fine mesh (the screenshot shown) it still doesnt match. You can try a very quick example of a simple pipe with a bend. Would you like me to upload my model?
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August 21, 2018, 17:52 |
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#6 |
Senior Member
Erik
Join Date: Feb 2011
Location: Earth (Land portion)
Posts: 1,183
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Just checking, is the position and orientation of the pipe elbow the same in both models?
There seems to be a pretty huge discrepancy here. |
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August 21, 2018, 17:54 |
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#7 |
New Member
Moustafa El-sawy
Join Date: Aug 2018
Posts: 4
Rep Power: 8 |
Yeah they are the same exact model. I am importing the geometry from CFD to mechanical using workbench. You are free to do a quick trial using a simple geometry. The results change with different mesh in mechanical but they never seem to match close enough to be reliable?
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February 1, 2022, 04:33 |
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#8 | |
New Member
power
Join Date: Dec 2021
Posts: 6
Rep Power: 4 |
Quote:
Hi Did you solve this problem? I am confronting the same issue. in my case, the pressure load which is plotted in Fluent is not the same as the imported pressure which is shown in Ansys Mechanical. |
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February 1, 2022, 09:47 |
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#9 |
Senior Member
Join Date: Jun 2009
Posts: 1,865
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Wrong forum?
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Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum. |
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February 2, 2022, 02:50 |
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#10 |
New Member
power
Join Date: Dec 2021
Posts: 6
Rep Power: 4 |
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Tags |
cfx, fsi, mechanical coupling, unidirectional |
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