[Zigainer]

Hey,

I just started my transient calculation and it run quite good.
I calculated 9 setps successfully (with normal residuals) but in my 10th timestep I get the following error after 12 of 15 iterations:

Hope you can help me. Could this be, because somebody else started a calculation on the same machine and it run out of memory?

----
edit: only chance from a previous (running without error) one is Turbulence Numerics : Option : First Order -> High Resolution

----


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

+--------------------------------------------------------------------+
| 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]

Been asked a million times, I really should write an FAQ on this.

Floating point error means your simulation has diverged. You need to improve numerical stability. To fix it consider smaller time steps, better initial conditions, tighter convergence and lots of other options.

[Zigainer]

Hey,

I can't believe that my calculation diverged.

Here is the part of the out-file:

================================================== ====================
| Timestepping Information |
----------------------------------------------------------------------
| Timestep | RMS Courant Number | Max Courant Number |
+----------------------+----------------------+----------------------+
| 5.0000E-02 | 999.99 | 999.99 |
----------------------------------------------------------------------

================================================== ====================
TIME STEP = 10 SIMULATION TIME = 5.0000E-01 CPU SECONDS = 5.386E+04
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 1 CPU SECONDS = 5.386E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.14 | 1.6E-05 | 5.9E-03 | 1.0E-01 ok|
| V-Mom | 1.17 | 5.5E-05 | 1.9E-02 | 1.2E-01 ok|
| W-Mom | 1.13 | 2.6E-05 | 7.6E-03 | 1.4E-01 ok|
| P-Mass | 0.91 | 1.3E-07 | 1.9E-05 | 10.2 6.0E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.85 | 3.3E-03 | 1.5E-01 | 3.0E-02 OK|
| T-Energy | 1.19 | 8.2E-04 | 2.0E-02 | 6.2 3.0E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 1.19 | 3.0E-05 | 8.8E-03 | 6.2 6.4E-02 OK|
| O-TurbFreq | 0.90 | 5.2E-06 | 2.1E-03 | 7.6 4.6E-05 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 2 CPU SECONDS = 5.425E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.83 | 1.4E-05 | 2.9E-03 | 1.1E-01 ok|
| V-Mom | 1.29 | 7.1E-05 | 1.7E-02 | 1.1E-02 OK|
| W-Mom | 0.88 | 2.3E-05 | 5.7E-03 | 1.2E-01 ok|
| P-Mass | 2.08 | 2.6E-07 | 2.7E-05 | 23.9 8.3E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.07 | 2.4E-04 | 1.3E-02 | 7.9E-02 OK|
| T-Energy | 0.30 | 2.4E-04 | 4.2E-03 | 16.5 7.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 1.46 | 4.4E-05 | 3.6E-03 | 11.4 2.9E-02 OK|
| O-TurbFreq | 9.17 | 4.7E-05 | 1.9E-03 | 7.6 5.6E-05 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 3 CPU SECONDS = 5.472E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.32 | 1.8E-05 | 4.2E-03 | 1.0E-01 ok|
| V-Mom | 0.69 | 4.9E-05 | 1.1E-02 | 9.4E-02 OK|
| W-Mom | 0.90 | 2.1E-05 | 3.4E-03 | 1.1E-01 ok|
| P-Mass | 1.23 | 3.2E-07 | 3.3E-05 | 14.8 6.8E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.88 | 2.1E-04 | 1.8E-02 | 9.9E-02 OK|
| T-Energy | 0.63 | 1.5E-04 | 3.3E-03 | 6.2 9.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.91 | 4.0E-05 | 8.2E-03 | 6.2 9.6E-02 OK|
| O-TurbFreq | 1.05 | 5.0E-05 | 3.6E-03 | 7.6 9.1E-05 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 4 CPU SECONDS = 5.510E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.03 | 1.8E-05 | 4.3E-03 | 1.0E-01 ok|
| V-Mom | 1.11 | 5.4E-05 | 1.6E-02 | 1.1E-01 ok|
| W-Mom | 1.18 | 2.4E-05 | 4.8E-03 | 1.2E-01 ok|
| P-Mass | 0.84 | 2.7E-07 | 3.3E-05 | 10.2 6.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.72 | 1.5E-04 | 2.4E-02 | 8.5E-02 OK|
| T-Energy | 0.23 | 3.5E-05 | 8.9E-04 | 6.2 8.5E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.73 | 2.9E-05 | 7.4E-03 | 6.2 8.3E-02 OK|
| O-TurbFreq | 0.28 | 1.4E-05 | 1.8E-03 | 7.6 1.1E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 5 CPU SECONDS = 5.548E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.78 | 1.4E-05 | 3.0E-03 | 1.0E-01 OK|
| V-Mom | 0.92 | 5.0E-05 | 1.1E-02 | 1.1E-01 ok|
| W-Mom | 0.93 | 2.3E-05 | 4.6E-03 | 1.3E-01 ok|
| P-Mass | 0.71 | 1.9E-07 | 2.5E-05 | 10.2 4.8E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.73 | 1.1E-04 | 1.8E-02 | 7.6E-02 OK|
| T-Energy | 0.57 | 2.0E-05 | 3.1E-04 | 6.2 7.6E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.83 | 2.4E-05 | 6.2E-03 | 6.2 7.5E-02 OK|
| O-TurbFreq | 0.53 | 7.6E-06 | 1.2E-03 | 7.6 1.6E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 6 CPU SECONDS = 5.585E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.91 | 1.3E-05 | 2.5E-03 | 1.1E-01 ok|
| V-Mom | 0.91 | 4.6E-05 | 9.7E-03 | 1.3E-01 ok|
| W-Mom | 0.83 | 1.9E-05 | 3.3E-03 | 1.5E-01 ok|
| P-Mass | 0.83 | 1.6E-07 | 2.1E-05 | 10.2 5.0E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.83 | 9.2E-05 | 1.9E-02 | 7.5E-02 OK|
| T-Energy | 0.45 | 8.8E-06 | 2.1E-04 | 6.2 7.5E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.95 | 2.3E-05 | 5.5E-03 | 6.2 7.7E-02 OK|
| O-TurbFreq | 0.75 | 5.7E-06 | 1.8E-03 | 7.6 2.3E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 7 CPU SECONDS = 5.623E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.15 | 1.5E-05 | 4.7E-03 | 1.1E-01 ok|
| V-Mom | 1.02 | 4.7E-05 | 1.3E-02 | 1.3E-01 ok|
| W-Mom | 1.05 | 2.0E-05 | 5.1E-03 | 1.4E-01 ok|
| P-Mass | 0.93 | 1.5E-07 | 1.6E-05 | 10.2 5.8E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 1.03 | 9.4E-05 | 2.3E-02 | 7.2E-02 OK|
| T-Energy | 0.68 | 6.0E-06 | 1.7E-04 | 6.2 7.2E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 1.25 | 2.9E-05 | 8.2E-03 | 6.2 7.3E-02 OK|
| O-TurbFreq | 0.98 | 5.5E-06 | 2.1E-03 | 7.6 2.7E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 8 CPU SECONDS = 5.660E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.15 | 1.7E-05 | 7.5E-03 | 9.9E-02 OK|
| V-Mom | 1.15 | 5.4E-05 | 2.1E-02 | 1.1E-01 ok|
| W-Mom | 1.21 | 2.4E-05 | 8.3E-03 | 1.2E-01 ok|
| P-Mass | 0.95 | 1.4E-07 | 2.0E-05 | 10.2 5.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 1.07 | 1.0E-04 | 2.4E-02 | 6.9E-02 OK|
| T-Energy | 0.86 | 5.1E-06 | 2.6E-04 | 6.2 6.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 1.12 | 3.3E-05 | 8.7E-03 | 6.2 6.5E-02 OK|
| O-TurbFreq | 0.88 | 4.9E-06 | 1.7E-03 | 7.6 2.5E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 9 CPU SECONDS = 5.698E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.95 | 1.6E-05 | 5.5E-03 | 9.5E-02 OK|
| V-Mom | 0.99 | 5.3E-05 | 1.5E-02 | 1.0E-01 ok|
| W-Mom | 1.13 | 2.7E-05 | 7.8E-03 | 1.2E-01 ok|
| P-Mass | 1.02 | 1.5E-07 | 1.7E-05 | 10.2 4.8E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.90 | 9.1E-05 | 1.8E-02 | 7.4E-02 OK|
| T-Energy | 0.95 | 4.9E-06 | 3.5E-04 | 6.2 7.4E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.86 | 2.8E-05 | 6.4E-03 | 6.2 6.3E-02 OK|
| O-TurbFreq | 0.79 | 3.9E-06 | 1.1E-03 | 7.6 2.4E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 10 CPU SECONDS = 5.735E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.85 | 1.4E-05 | 2.9E-03 | 1.0E-01 ok|
| V-Mom | 0.90 | 4.8E-05 | 1.3E-02 | 1.3E-01 ok|
| W-Mom | 0.85 | 2.3E-05 | 5.6E-03 | 1.4E-01 ok|
| P-Mass | 1.07 | 1.6E-07 | 1.7E-05 | 10.2 4.4E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.92 | 8.4E-05 | 1.4E-02 | 9.9E-02 OK|
| T-Energy | 0.97 | 4.7E-06 | 2.5E-04 | 6.2 9.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 0.84 | 2.4E-05 | 3.1E-03 | 6.2 6.7E-02 OK|
| O-TurbFreq | 1.19 | 4.6E-06 | 1.8E-03 | 7.6 2.4E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 11 CPU SECONDS = 5.773E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.10 | 1.5E-05 | 4.1E-03 | 1.0E-01 ok|
| V-Mom | 1.05 | 5.0E-05 | 1.1E-02 | 1.4E-01 ok|
| W-Mom | 0.79 | 1.8E-05 | 3.6E-03 | 1.3E-01 ok|
| P-Mass | 0.98 | 1.5E-07 | 2.1E-05 | 10.2 5.3E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 1.12 | 9.4E-05 | 1.6E-02 | 2.9E-02 OK|
| T-Energy | 0.96 | 4.5E-06 | 2.4E-04 | 11.3 2.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 1.06 | 2.5E-05 | 5.7E-03 | 6.2 6.8E-02 OK|
| O-TurbFreq | 1.06 | 4.9E-06 | 2.0E-03 | 7.6 1.8E-04 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 12 CPU SECONDS = 5.810E+04
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.01 | 1.5E-05 | 3.6E-03 | 9.4E-02 OK|
| V-Mom | 1.12 | 5.6E-05 | 1.2E-02 | 1.2E-01 ok|
| W-Mom | 1.18 | 2.1E-05 | 4.5E-03 | 1.2E-01 ok|
| P-Mass | 0.90 | 1.4E-07 | 2.3E-05 | 10.2 5.3E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 1.08 | 1.0E-04 | 2.4E-02 | 9.1E-02 OK|
| T-Energy | 1.06 | 4.8E-06 | 2.9E-04 | 6.2 9.1E-02 OK|
+----------------------+------+---------+---------+------------------+

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

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

[Keppi]

Hi Zigainer!

I'm not an expert of transient simulations, not even ANSYS. You should listen to ghorrocks. But I had the same error recently, and there are many good possible solutions on this forum. I advice you to use the search option.
Also, according to your last reply, I would decrease the timestep, instead of increasing the coefficient loops. Double precision may can also help, to avoid rounding errors.
Another possible solution of this problem is to start your transient simulation from a converged steady state solution.

[Zigainer]

Hey,

my calculation starts from a converged stead state calculation with all data from the first timestep.
And again, I had a calculation (same setup) which was running.
The only change was in "solver control" -> Turbulence Numerics -> from First Order to High Resolution.
And I can't believe that this small change destroyed my convergence.

[ghorrocks]

And I can't believe

What is this? The X-Files or something? Trust me, and believe. It is diverging. I have seen it a zillion times.

And in this case you seem to be using a massive time step so the first thing I would try is running a time step far smaller than you currently.

[Zigainer]

Hey,

I tried a timestep of 0.01 (one fifth of original one) and it also interrupted.
and again the only change to a running one is turbulence numerics.
And if I watch the residual I can't see a divergence sorry..... residual are getting smaller and smaller and then the error occurce

[ghorrocks]

You need a much smaller timestep than that.

Floating point error divergences do not always show up in residuals.

[Zigainer]

Alright thanks.
I actually do not have enough time for a smaller timestep.
The calculation for the 0.01s timestep would run almost 1 month.
So a smaller timestep is not really possible. I stick to the First Order Turbulence Numerics.

[ghorrocks]

Do you want it to run or not? Up to you.

You will probably be able to use some small timesteps to start it off and increase them from there. Adaptive time steps (adapting to 3-5 coeff loops per iteration) is very useful here as it does it automatically.

[Zigainer]

Meanwhile I've got some changes (inlet channel before the ribbed channel) and with these simulation is no problem. Even with the "large" timestep of 0.05s

But thanks for your help!!!

[ghorrocks]

Why didn't you say that before? So it is more likely then you have a setup problem with this simulation but not the other.

Can you post an image of both geometries?

[Zigainer]

Originally Posted by ghorrocks

Can you post an image of both geometries?

The ribbed channel part is the same for both. The new calculation just got an extra un-ribbed-inlet-channel.
The calculation which is not running doesn't use a velocity- and temperature-profile at the inlet.

---edit:
btw its a conjugated calculation

[ghorrocks]

If the longer simulation runs OK then it is likely to be something wrong with your setup of the shorter one. If you also changed the inlet BC type between runs then that is likely to be the problem.

[Zigainer]

The INLET condition is the same for both simualtions.
The new longer calcualtion is running, so tahts fine for me. I don't need the shorter one, anyway. There've been an other problem with velocity-profil anyway.
Thanks for your help.