[amsys]

Dear all,

I have a pipe which is rigid and a patch on the surface of this tube which is deformable/flexible. I want to investigate the interaction of this flexible part with fluid that is pumped through the pipe, so I can see how the flow of the fluid is affected by the deformation of the patch and vice versa (fluid structure interaction). I am coupling the CFX analysis system of ANSYS with the transient structural analysis system. The boundary conditions are not complex. The inlet of the the tube which is an opening has a relative pressure of 100 Pa where the flow direction is normal to the boundary condition, the outlet of the tube which is also an opening has a relative pressure of 0 Pa where the flow direction is also normal to the boundary condition. The boundary conditions of the walls (fluid structure interaction interface) are no slip walls where the walls are smooth and their velocity is relative to the mesh motion.

I have imported the geometry as one body from SolidWorks before separating it into 3 separate body parts [the deformable patch (this is two parts separated with a 1mm gap http://tinypic.com/r/2hnndps/8), the tube, and the surrounding body], I made the patch and pipe a surface body and the surrounding part a solid body before using the fill tool to create the fluid region. When meshing in transient I suppress the fluid domain part created from the fill tool and when meshing in CFX I suppress all but the fluid region. See attached images of geometry http://tinypic.com/r/jgs7ib/8 http://tinypic.com/r/5n5dvl/8. When I try running for a solution I get the following error message and I believe it may be as a result of how I am separating the body into parts or meshing. Any suggestions or advice would be very helpful. Thanks.


-----------------------

No isolated fluid regions were found.


+--------------------------------------------------------------------+
| ********* WARNING ********* |
| Within the current MFX simulation, unmapped vertices are present |
| on the Fluid-Solid interface: |
| FSI interafce |
| Please review the ANSYS.stdout file for further information. |
| Default boundary conditions will be applied for these unmapped |
| vertices, which implies "Unspecified" for Mesh Motion. To try a |
| coupled mesh displacement instead, set the expert parameter: |
| mfx unmapped bc option = 2 |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| The Equations Solved in This Calculation |
+--------------------------------------------------------------------+

Subsystem : Mesh Displacement

X-Disp
Y-Disp
Z-Disp

Subsystem : Momentum and Mass

U-Mom
V-Mom
W-Mom
P-Mass

Subsystem : TurbKE and Diss.K

K-TurbKE
E-Diss.K

CFD Solver started: Wed Sep 02 10:29:52 2015


+--------------------------------------------------------------------+
| Convergence History |
+--------------------------------------------------------------------+

================================================== ====================
| COUPLING STEP = 1 |
================================================== ====================

----------------------------------------------------------------------
| COUPLING/STAGGER ITERATION = 1 |
----------------------------------------------------------------------

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

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| cplg_SendCommand failed to send the command: ERROR -- CFX encount- |
| ered the error: Read. Fatal error occurred when requesting Total |
| Mesh Displacement for FSI interafce. |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Stopped in routine cplg_SendCommand |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| An error has occurred in cfx5solve: |
| |
| The ANSYS CFX solver exited with return code 1. No results file |
| has been created. |
+--------------------------------------------------------------------+

End of solution stage.

+--------------------------------------------------------------------+
| An error has occurred in cfx5solve: |
| |
| ANSYS Solver terminated with return code 256

[stumpy]

The error in CFX is just saying the structural solver failed. I would guess the pressures passed to the structure caused too much deformation for the structural solver to handle in a single step. Check that you can solve a structural-only model with a representative pressure load applied before you try the FSI solution.