FSI Errors give Highly distorted Element and Solver Pivot error

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Nk_ad posted this 15 October 2018

I am simulating FSI of multiphase flow (upward flow) through a 2inch pipe with bend in ANSYS 17. The mesh is triangular 293608 elements and the only supports are fixed supports at the 2 ends of the pipe. Step size for the simulation is 1E-06. When I run the simulation, I get this the pop message:

The program can't start because AnsMPI.dll is missing from your computer. Try reinstalling the program to fix this problem.

But the simulation keeps attempting to run until it eventually stops with the error message below

DP 0) Element 241459 located in Body "Pipe Structure" (and maybe other elements) has become highly distorted.  You may select the offending object and/or geometry via RMB on this warning in the Messages window.  Excessive distortion of elements is usually a symptom indicating the need for corrective action elsewhere.  Try incrementing the load more slowly (increase the number of substeps or decrease the time step size).  You may need to improve your mesh to obtain elements with better aspect ratios.  Also consider the behavior of materials, contact pairs, and/or constraint equations.  If this message appears in the first iteration of first substep, be sure to perform element shape checking. Named Selections for the offending element can be created via the Identify Element Violations property on the Solution Information Object.

When I repeat this simulation with a smaller number of mesh element 67000 (quads and wedges) in ANSYS 18, the error is:

"(DP 0) A solver pivot warning or error has been detected in the UY degree of freedom of node 10890 located in Pipe Structure. This is usually a result of an ill conditioned matrix possibly due to unreasonable material properties, an under constrained model, or contact related issues.  Check results carefully. You may select the offending object and/or geometry via RMB on this warning in the Messages window."

Please I will really appreciate any help on how to solve this problem.

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kkanade posted this 16 October 2018

Hello,

Please try to use R19.1 which is latest available. 

Please try to run separately fluids and structure separately. Make sure that they run ok. Then only go for FSI. 

You can check following link for FSI. 

Hope this helps. 

 

Regards,

Keyur

 

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Nk_ad posted this 17 October 2018

Hi,

Thank you for your response.

I can't have access to ANSYS 19.1 currently.

But if ANSYS 18 and 17 can run 2-way FSI through pipe elbow correctly, then I will have to focus on finding out if my structural and fluids systems are running OK separately.

Presently the transient structural system has run successfully so I am on to the fluids system.

Regards

Nkem

kkanade posted this 17 October 2018

Yes, please check fluids rum and then update. 

Regards,

Keyur

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Nk_ad posted this 22 October 2018

Hi,

I have confirmed that both the transient structural system and the fluid system run successfully.

Now, when I couple the two systems the errors become:

"Error: No journal response to dialogue box message. warning: invalid initial data. Probably available initial data file is not compatible to fluent's current mesh. using basic initialization based on settings"

"(DP 0) TableView:Exception during Table Selection: Exception of type 'System.OutOfMemoryException' was thrown."

 

I await your kind responses.

 

Nkem

kkanade posted this 22 October 2018

Hello, 

Are you running design points? Can you please check it without design points

Regards,

Keyur

Nk_ad posted this 25 October 2018

Hi,

I don't really know what you mean by design points but I used ICEM to mesh the fluid system (see attached image ANSYS 18_1) and the simulation is in ANSYS 18.1. ANSYS 18_1

 

On the other hand, running the same simulation with Fluent mesh and in ANSYS 17.0 gives the error in the 2 attached images below.

ANSYS 17_1

ANSYS 17_2

All the systems run successfully individually. They only fail when I couple them.

I could attach the workbench files of the project if you would like to see it.

 

Thanks for your kind responses

Regards

Nkem

 

 

kkanade posted this 25 October 2018

Hi,

Can you please check if you have any spaces or special characters in your file name or folder/subfolder names. If so, can you please rename them. 

Can you please use latest version R19.2. 

Also please use workbench meshing as shown in video.

Regards,

Keyur

 

Jirong posted this 3 weeks ago

 Hi All,

I am simulating a 2 way FSI problem (mitral valve) with system coupling. But i got error said high distortion element. I set velocity-inlet, and chose smoothing and remesh in dynamic mesh zone. And used isotropic elasticity for mechanical part. I'm using version 19.1. I even failed with setting 0m/s velocity inlet. 

Can anyone give some advice? 

 

Thanks,

Jirong

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