[sajad.mojatahedi]

Hello, dear experts
The simulation stops after some time and the graph(stability limit & Time-step size) reaches zero, what could be the reason for this?

[RobAM]

There might be some information in the solver message window - what does it say there?

[sajad.mojatahedi]

I put part of the messages inside (solver message window):

restarting cycle with smaller time step
1.27732E+03 12960 4.59E-03 1.02E-02/fs 1 4.25E-01 8.4315E-01 +6.46E-03 0.54 07:40:42 71 00:39:56
convective flux exceeded stability limit
at t= 1.2781E+03 cycle= 13058 iter= 2 delt= 8.2209E-03 mesh block 1
restarting cycle with smaller time step
1.27936E+03 13232 5.41E-03 1.02E-02/fs 1 6.50E-01 8.4325E-01 +6.49E-03 0.54 07:50:43 71 00:49:57
convective flux exceeded stability limit
at t= 1.2800E+03 cycle= 13310 iter= 2 delt= 7.9311E-03 mesh block 1
restarting cycle with smaller time step
convective flux exceeded stability limit
at t= 1.2808E+03 cycle= 13412 iter= 2 delt= 1.0203E-02 mesh block 1
restarting cycle with smaller time step
1.28134E+03 13504 3.19E-03 5.55E-03/sy 1 2.92E-01 8.4322E-01 +6.46E-03 0.54 08:00:45 73 00:59:58
1.28211E+03 13808 9.85E-04 9.85E-04/vs 1 1.08E-01 8.4321E-01 +6.48E-03 0.54 08:10:45 69 01:09:59
1.28234E+03 14114 6.13E-04 6.13E-04/vs 1 1.25E-01 8.4322E-01 +6.47E-03 0.54 08:20:47 71 01:20:00
1.28251E+03 14419 4.78E-04 4.78E-04/vs 1 2.81E-02 8.4322E-01 +6.46E-03 0.54 08:30:47 68 01:30:01
1.28264E+03 14724 4.03E-04 4.03E-04/vs 1 2.71E-02 8.4323E-01 +6.46E-03 0.54 08:40:48 54 01:40:01
1.28276E+03 15029 3.55E-04 3.55E-04/vs 1 4.68E-02 8.4323E-01 +6.45E-03 0.54 08:50:49 54 01:50:02
1.28286E+03 15335 3.21E-04 3.21E-04/vs 1 2.53E-02 8.4323E-01 +6.45E-03 0.54 09:00:49 51 02:00:03
1.28295E+03 15642 2.94E-04 2.94E-04/vs 1 3.93E-02 8.4323E-01 +6.44E-03 0.54 09:10:49 52 02:10:03
1.28304E+03 15949 2.74E-04 2.74E-04/vs 1 1.96E-02 8.4323E-01 +6.44E-03 0.54 09:20:50 54 02:20:03
1.28312E+03 16270 2.56E-04 2.56E-04/vs 1 1.45E-02 8.4323E-01 +6.43E-03 0.54 09:30:51 50 02:30:05
1.28320E+03 16590 2.41E-04 2.41E-04/vs 1 2.99E-02 8.4323E-01 +6.43E-03 0.54 09:40:52 52 02:40:05
1.28328E+03 16898 2.30E-04 2.30E-04/vs 1 1.55E-02 8.4323E-01 +6.42E-03 0.54 09:50:53 54 02:50:06
1.28335E+03 17203 2.19E-04 2.19E-04/vs 1 1.22E-02 8.4323E-01 +6.42E-03 0.54 10:00:53 54 03:00:07

[sajad.mojatahedi]

The part marked with blue color in the attached image is different among all the messages displayed in the (solver message window)!!!!
At first, I thought it might be a hardware problem, but I tried it with another system and both systems have a problem during simulation when they reach 1280 seconds.

[sajad.mojatahedi]

In order to reach the state of full development in the scouring process of the bridge support, I extended the simulation time to 1200 seconds, of course, in several steps and through the use of the restart time section in four 300-second steps... due to not being realized, I had to I continued until 1500 seconds
I had no problem until 1200 seconds, but after that I have problems at 1280 seconds
According to the messages of the solver window, it is clear that the time steps are larger before 1280 seconds, but at 1280 seconds, it seems that the calculation steps become smaller and the simulation time becomes very long.

[RobAM]

My best guess would be that there is something wrong with your convection settings.

[sajad.mojatahedi]

Hello, thank you for your time
In which part of the software did you put the convection settings, I did not understand what you mean

[RobAM]

Although it's an older version of FLOW-3D, this might help:
https://docshare.tips/exercises-flow...25e8b4840.html