Thursday, August 29, 2013

FSI error with Ansys Fluent or CFX

If you're getting one of the following errors while performing a FSI ( Fluid structure interaction ) simulation using ansys
Fluent coupling error :
 +====================================================================+
 |                      System Coupling Exception                     |
 +====================================================================+
 | Origin            : Transient Structural (Solution)                |
 | Error Code        : 2                                              |
 | Error Description :                                                |
 |    One or more elements have become highly distorted.  Excessive   |
 |   distortion of elements is usually a symptom indicating the need  |
 |   for corrective action elsewhere.  Try ramping the load up        |
 |   instead of step applying the load (KBC,1).                       |
 +====================================================================+

CFX coupling error :
 +--------------------------------------------------------------------+
 | ERROR #001100279 has occurred in subroutine ErrAction.             |
 | Message:                                                           |
 | CFX encountered the error: Read.  Fatal error occurred when reque- |
 | sting Total Mesh Displacement for FSI.                             |
 |                                                                    |
 |                                                                    |
 |                                                                    |
 |                                                                    |
 +--------------------------------------------------------------------+

This may occur if your solid is largely deforming at the very first step under your fluid pressure.
Remember that fluent has an operation pressure, cfx has a reference pressure too. All pressures you define are relative to this reference pressure. So it may cause a pressure increase in your model and cause a huge displacement resulting the above error.
Another reason might be if you're defining velocity inlet in wrong pressure. For example consider a pipe with X axis. Now if you wrongly define the velocity inlet toward Y or Z instead of X axis, the reduction in velocity at wall locations will cause a high pressure increase and same story.

Mos

Thursday, August 22, 2013

Fluent FSI Error : Unassigned interface zone detected for interface 6.

If you're trying to perform a FSI simulation using Ansys Fluent & Mechanical and getting the following error when you click on "Check Mesh" :

WARNING: Unassigned interface zone detected for interface 6.

WARNING: Mesh check failed.

To get more detailed information about the mesh check failure
increase the mesh check verbosity via the TUI command
/mesh/check-verbosity.

The reason of the above error is that type of BC which is set for your FSI interface is set to "Interface" while it should be "Wall" with an applied dynamic mesh on it...

Monday, August 19, 2013

Adina systems : ***INPUT ERROR: No node found in BCD X

This is my first Mechanical Engineering Post !

I was working with Adina systems FEM software performing a FSI simulation (Fluid Structure Interaction).
I received ' ***INPUT ERROR: No node found in BCD 1' when tried to generate the DATA file.

After some R&D I found that this error occurs when you've defined the FSI Boundary on wrong body ( e.g. Solid body instead of Fluid one )

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