[funnier]

I am running transident CFD simulation of rocket. the simulation time was given 58 second but it failed in 8 second. Can anyone help me to understand the reason of faliure?

Rocket dimenssion

The length of rocket is 5.1 meter and base diameter is 559 mm.




Fuid domain

36 meter and width 41 meter, and downstream length is 20.8 meter.

CFX Boundary Condition


The geometry is 2d planner and extrude distance is 0.5.

Boundary condition is Inlet, Outlet, Fahrfield, Fluid Symmetry(both side selected as one symmetry), Rocket Symmetry(both side selected as one symmetry), Inner wall of rocket, and Interface (for both fluid and rocket).

Pressure, velocity and Temperature function is asssigned

In the expert parameter > Convergence control > Max continuity loop is set to 2.


Here is the OutFile (Whole OutFile Download)


COEFFICIENT LOOP ITERATION = 97 CPU SECONDS = 8.597E+05
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.51 | 4.1E-04 | 1.2E-01 | 2.5E-03 OK|
| V-Mom | 0.93 | 1.9E-05 | 4.3E-03 | 8.7E-02 OK|
| W-Mom | 0.00 | 0.0E+00 | 0.0E+00 | 0.0E+00 OK|
| P-Mass | 0.88 | 2.3E-04 | 7.7E-02 | 5.1 1.1E-02 OK|
+----------------------+------+---------+---------+------------------+
| H-Energy | 0.70 | 1.3E-04 | 1.4E-02 | 7.8E-04 OK|
| T-Energy | 1.08 | 2.4E-06 | 9.5E-05 | 5.9 7.8E-04 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 1.09 | 9.6E-06 | 9.7E-04 | 15.4 7.9E-02 OK|
| O-TurbFreq | 1.01 | 8.1E-06 | 1.1E-03 | 10.8 6.2E-05 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| P-Mass | 0.37 | 8.3E-05 | 2.1E-02 | 5.1 2.5E-02 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 98 CPU SECONDS = 8.598E+05
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 1.38 | 5.7E-04 | 1.5E-01 | 1.0E-02 OK|
| V-Mom | 0.55 | 1.1E-05 | 2.1E-03 | 1.4E+01 F |
| W-Mom | 0.00 | 0.0E+00 | 0.0E+00 | 0.0E+00 OK|
| P-Mass | 0.03 | 7.9E-06 | 1.6E-03 | 13.3 2.9E-01 ok|
+----------------------+------+---------+---------+------------------+
| H-Energy | 1.71 | 2.2E-04 | 4.7E-02 | 2.0E-03 OK|
| T-Energy | 4.45 | 1.1E-05 | 1.3E-03 | 5.9 2.0E-03 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE | 2.90 | 2.8E-05 | 4.0E-03 | 10.6 4.8E-02 OK|
| O-TurbFreq | 4.88 | 3.9E-05 | 2.9E-02 | 10.8 2.3E-05 OK|
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| P-Mass | 0.04 | 2.8E-07 | 4.5E-05 | 9.2 1.4E+01 F |
+----------------------+------+---------+---------+------------------+
----------------------------------------------------------------------
COEFFICIENT LOOP ITERATION = 99 CPU SECONDS = 8.598E+05
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+
| U-Mom | 0.62 | 3.5E-04 | 5.3E-02 | 1.2E-01 ok|
| V-Mom |13.64 | 1.5E-04 | 2.1E-02 | 1.8E-01 ok|
| W-Mom | 0.00 | 0.0E+00 | 0.0E+00 | 0.0E+00 OK|
| P-Mass |30.23 | 2.4E-04 | 4.3E-02 | 9.2 1.0E+00 F |
+----------------------+------+---------+---------+------------------+
+--------------------------------------------------------------------+
| ****** Notice ****** |
| The non-dimensional near wall temperature (T+) has been clipped |
| for calculation of Wall Heat Transfer Coefficient. |
| |
| Boundary Condition : FluidSolid Side 2 |
| T+ clip value = 1.0000E-10 |
| |
| If this situation persists and you are using the High Speed Model, |
| consider enabling Mach number based blending between low speed and |
| high speed wall functions. You can do so by specifying a Mach |
| number threshold as follows: |
| |
| EXPERT PARAMETERS: |
| highspeed wf mach threshold = 0.1 # default=0.0 (off) |
| END |
+--------------------------------------------------------------------+
| H-Energy | 6.63 | 1.5E-03 | 6.0E-01 | 9.9E-02 OK|
| T-Energy |99.99 | 7.7E-03 | 9.6E-01 | 5.9 9.9E-02 OK|
+----------------------+------+---------+---------+------------------+
| K-TurbKE |50.37 | 1.4E-03 | 2.6E-01 | 5.8 1.4E-05 OK|
| O-TurbFreq |70.02 | 2.8E-03 | 6.9E-01 | 10.8 1.5E-09 OK|
+----------------------+------+---------+---------+------------------+

Parallel run: Received message from follower
--------------------------------------------
Follower partition: 2
Follower routine : get_TWFTFC
Leader location : End of Continuity Loop
Message label : 009100015
Message follows below - :
+--------------------------------------------------------------------+
| ****** Notice ****** |
| The non-dimensional near wall temperature (T+) has been clipped |
| for calculation of Wall Heat Transfer Coefficient. |
| |
| Boundary Condition : FluidSolid Side 2 |
| T+ clip value = 1.0000E-10 |
| |
| If this situation persists and you are using the High Speed Model, |
| consider enabling Mach number based blending between low speed and |
| high speed wall functions. You can do so by specifying a Mach |
| number threshold as follows: |
| |
| EXPERT PARAMETERS: |
| highspeed wf mach threshold = 0.1 # default=0.0 (off) |
| END |
+--------------------------------------------------------------------+

Parallel run: Received message from follower
--------------------------------------------
Follower partition: 3
Follower routine : get_TWFTFC
Leader location : End of Continuity Loop
Message label : 009100015
Message follows below - :
+--------------------------------------------------------------------+
| ****** Notice ****** |
| The non-dimensional near wall temperature (T+) has been clipped |
| for calculation of Wall Heat Transfer Coefficient. |
| |
| Boundary Condition : FluidSolid Side 2 |
| T+ clip value = 1.0000E-10 |
| |
| If this situation persists and you are using the High Speed Model, |
| consider enabling Mach number based blending between low speed and |
| high speed wall functions. You can do so by specifying a Mach |
| number threshold as follows: |
| |
| EXPERT PARAMETERS: |
| highspeed wf mach threshold = 0.1 # default=0.0 (off) |
| END |
+--------------------------------------------------------------------+
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+

+--------------------------------------------------------------------+
| ERROR #004100018 has occurred in subroutine FINMES. |
| Message: |
| Fatal overflow in linear solver. |
+--------------------------------------------------------------------+
End of solution stage.

+--------------------------------------------------------------------+
| The following transient and backup files written by the ANSYS CFX |
| solver have been saved in the directory |
| C:/Project/bluntnodegree_pending/dp0_CFX_Solution-1/RocketWithExpP- |
| aTrans_001: |
| |
| 929_full.trn, 732_full.trn, 58_full.trn, 549_full.trn, |
| 381_full.trn, 3048_full.trn, 3000_full.bak, 2725_full.trn, |
| 2420_full.trn, 241_full.trn, 2132_full.trn, 1860_full.trn, |
| 1605_full.trn, 14_full.trn, 1365_full.trn, 134_full.trn, |
| 1140_full.trn, 0_full.trn |
+--------------------------------------------------------------------+


+--------------------------------------------------------------------+
| The following user files have been saved in the directory |
| C:/Project/bluntnodegree_pending/dp0_CFX_Solution-1/RocketWithExpP- |
| aTrans_001: |
| |
| pids, mon |
+--------------------------------------------------------------------+


+--------------------------------------------------------------------+
| For CFX runs launched from Workbench, the final locations of |
| directories and files generated may differ from those shown. |
+--------------------------------------------------------------------+


+--------------------------------------------------------------------+
| Warning! |
| |
| After waiting for 60 seconds, 1 solver manager process(es) appear |
| not to have noticed that this run has ended. You may get errors |
| removing some files if they are still open in the solver manager. |
+--------------------------------------------------------------------+


This run of the ANSYS CFX Solver has finished.

[Opaque]

Are you running a transient model?

did you run the steady model as an initial condition?

Which timestep did you use for integration?

97 coefficient loop iterations indicate the setup is incorrect somewhere.

[Gert-Jan]

- Lets start basic: What question do you want to answer when doing CFD on the rocket?
- Why do you include the solid domain?
- Why do you run transient? Did you try steady state as Opaque already asked?
- It looks like you select all relevant physics starting from the first step. Why do you try to hit the roof in one step? WHy not step by step?
- Did you try a simple case first, Meaning: Steady state, only air at a low velocity?
- It this runs, did you increase the velocity further and further, restarting from a converged case?