[silvia_petkova]

Hello,
I'd like to ask you for help, because I am trying desperately to solve my complicated model in Ansys Workbench. I am using Ansys MuliField external soler coupling, because the examined problem concerns Fluid - Pipe - Soil interaction.
The model consists to submodel :
· Structural , prepared in WB. It is soil body ( block 20/6/11m ), which enclouse steel pipe - D=1m and thickness 15mm.
flFlexible analys steps are prepared in WB ( springs with stiffnes and damping connect the Soil Body to Ground along the four enclosure face; general joint has been put on the lower face and seismic support excitation - acceleration is applyed through it in joint condition, than Ansys input file has been written)
· the other model is the model of the fluid and it has been prepared and meshed with CFX Mesh, than the simulation type and the other steps are made and the coupled solver has been strarted, but the solution breaks off..................
Ansys Out File:
*** WARNING *** CP = 1284.824 TIME= 16:42:47
Pivoting option activated for Sparse Direct Solver. The memory
required may greatly exceed predicted amount. In that event rerun
with increased memory using -m option (refer to the Basic Analysis
Procedures Guide, Ch. 19).
Sparse solver maximum pivot= 6.872610448E+27 at node 48 UX.
Sparse solver minimum pivot= -1.49352841E+30 at node 81283 ROTZ.
Sparse solver minimum pivot in absolute value= 370396.354 at node 2074
UZ.

*** WARNING *** CP = 1549.449 TIME= 16:47:23
There are 1987 small equation solver pivot terms.
EQUIL ITER 1 COMPLETED. NEW TRIANG MATRIX. MAX DOF INC= -53.75

*** ERROR *** CP = 1554.378 TIME= 16:48:49
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). 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
run shape checking of elements.


*** WARNING *** CP = 1554.394 TIME= 16:48:49
The unconverged solution (identified as time 0.5 substep 999999) is
output for analysis debug purposes. Results should not be used for
any other purpose.

( CDF ) out file:

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| cplg_SendCommand failed to send the command: NEXTSP

I will be very grateful if you can Help me, thank you very much in advance!

Silvia Petkova

[ghorrocks]

The error message seems obvious to me - your mesh has moved excessively and the mesh quality is poor. This means the solver has problems converging. You will need to do some remeshing.

[silvia_petkova]

Thank you very much for the advice,
but I have already remeshed my model 10 times, well I might don't do this in the right way... I'd like to aks you, if know whether this that whole mesh of the fluid, preduced in WB - Mesh-Edit
in CFX Mesh consists of Ansys Element Type "Mesh200" and as far as I understand this
element is a "mesh-only" element, contributing nothing to the solution. Well is there a
way to change the type of Ansys element in Workbench, for example with fluid142 and do
you think if this would be helpful to overcome the error : *** ERROR *** One or more
elements have become highly distorted!
thanks again, best regards!

[ghorrocks]

No, you misunderstand me. I mean when the mesh is becoming distorted you interpolate your results onto a new, high quality mesh and resume the simulation from there. You remesh as the simulation proceeds.