[AS_Aero]

Hello All

Can I use opening boundary condition at Inlet with pressure as my input condition.
When I use Inlet Boundary condition the solver is crashing saying overflow and the mach number is going very high and the wall is creating and the simulation crashes. Its for axial fan simulation. And is it OK to use the Opening boundary condition at Inlet ? As we are using Opening condition for Outlet domain.

Thanks

[AS_Aero]

Even after changing to Opening boundary condition after some iterations, my simulation is crashing saying

+--------------------------------------------------------------------+

================================================== ====================
OUTER LOOP ITERATION = 138 CPU SECONDS = 3.915E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| c_fpx_handler: Floating point exception: Overflow |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

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

+--------------------------------------------------------------------+
| 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.

[ghorrocks]

FAQ: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F

Also read the CFX documentation on choice of boundary conditions, and the best practises guide for turbomachinery.

[AS_Aero]

Perfect Thanks a lot for your link. The problem is I only changed the fan domain and the now I have problem with convergence
1. It says a wall has placed at inlet and finally it has blown up with high mach number and overflow has happend and crashed.
2. I made it opening and still it has crashed with overblow.
Only thing that I have changed was the Turbogrid mesh for fan blade domain.

[ghorrocks]

This means your model is very numerically unstable and it is diverging. The FAQ describes some tips (also the two CFX doco links are very important as well), but it usually boils down to:
1) improve mesh quality
2) smaller time steps
3) double precision numerics
4) better initial condition