Ansys CFD Post Mesh Check
 

Hallo All

I have an issue with my fan simulation where my simulation blows up due to some negative volume error. In my output file which was generated after 100 iterations where my simulation crashed and there was an error message for negative volume and this is clearly coming from my Axial blade mesh that I did in Turbo grid. My concern how to solve this
1. how to visualize this negative volume in CFD post (the error gives the negative volume location)
2. How to solve this in Turbogrid (al though turbogrid creates the mesh and it doesnt show any negative volume in my mesh analysis.

You can create a point by coordinates in CFD post to vizualize the location.
To fix the mesh - you say it blows up some 100 iterations into the simulation. I assume it wouldn't even run with negativ elements in the first place, so are you deforming your mesh during the run? If yes, the mesh displacement variables in Post near the negativ volume location and see if the values are reasonable. Maybe you can improve the situation by allowing mesh motion on some boundaries (like allowing parallel to face or circumferentially).

No my mesh is not deformed during the run. I had a warning during the solver run
like below
+--------------------------------------------------------------------+
| Topology Simplification |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ****** Warning ****** |
| |
| Topology simplification is activated with the following |
| restrictions: |
| |
| - Mesh regions referenced only within User Fortran and NOT |
| in the command file will cause the solver to stop. |
| - The solver will stop during any "Edit Run in Progress" step |
| if new 2D regions are referenced. |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #002100011 has occurred in subroutine Out_NegVol. |
| Message: |
| A negative SECTOR volume has been detected. Execution will proceed |
| but this is a possible cause of robustness problems. |
| The location of the first negative volume is reported below. |
| Volume : -0.1514E-13 |
| Location : ( 0.20235E+00, 0.47428E-01, -0.33304E-01) |
| This warning may be made fatal by setting the expert parameter |
| 'negative volume option = 1'. |
+---------------------------
+--------------------------------------------------------------------+
| Mesh Statistics |
+--------------------------------------------------------------------+
| Domain Name | Orthog. Angle | Exp. Factor | Aspect Ratio |
+----------------------+---------------+--------------+--------------+
| | Minimum [deg] | Maximum | Maximum |
+----------------------+---------------+--------------+--------------+
| FLD_Fan | 6.8 ! | 44 ! | 3878 OK |
| FLD_Inlet | 41.6 ok | 45 ! | 98 OK |
| FLD_Outlet | 40.6 ok | 51 ! | 25 OK |
| Global | 6.8 ! | 51 ! | 3878 OK |
+----------------------+---------------+--------------+--------------+
| | %! %ok %OK | %! %ok %OK | %! %ok %OK |
+----------------------+---------------+--------------+--------------+
| FLD_Fan | 2 19 79 | <1 <1 100 | 0 0 100 |
| FLD_Inlet | 0 <1 100 | <1 3 97 | 0 0 100 |
| FLD_Outlet | 0 1 99 | <1 2 98 | 0 0 100 |
| Global | 1 8 91 | <1 1 99 | 0 0 100 |
+----------------------+---------------+--------------+--------------+

....
+----------------------+------+---------+---------+------------------+
| H-Energy | 1.33 | 1.0E-03 | 3.9E-01 | 5.6 8.8E-03 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.81 | 2.1E-03 | 1.7E-01 | 5.6 2.1E-04 OK|
| O-TurbFreq | 0.64 | 1.3E-02 | 9.8E-01 | 20.6 6.5E-11 OK|
+----------------------+------+---------+---------+------------------+
+--------------------------------------------------------------------+
| Notice: The maximum Mach number is 4.797E+05. |
+--------------------------------------------------------------------+

================================================== ====================
OUTER LOOP ITERATION = 140 CPU SECONDS = 3.285E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+

Parallel run: Received message from slave
-----------------------------------------
Slave partition : 11
Slave routine : ErrAction
Master location : Message Handler
Message label : 001100279
Message follows below - :

+--------------------------------------------------------------------+
| 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 |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine MESG_RETRIEVE. |
| Message: |
| Stopping the run due to error(s) reported above |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

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

You said TGrid detects no negative volumes, ok. But your Minimum Angles are too low anyway and should be reported in TGrid. I don't know what the actual minimum tolerable angle is for cfx but I feel like 15 deg. You have 6.8.

I assume the overflow and illegal mach number results from that, if not, the BCs need to be checked too.