Learning Forum

[Danielgkh]

Hi everyone,

So here's my case. In order to monitor a point in my simulation, I had set a new definition and chose both report to file and report to plot. Then I ran my simulation as normal, and the plot did show up properly. All the plot is then automatically saved in OUT file type.

However, when I reopen the simulation the next day, I am unable to report plot anymore. It says, there is no data available for this plot object. I am also unable to continue running the simulation from the previous point as it will ask me to overwrite the data.

The weird thing is, I am pretty sure the data is still there, as I am able to load and plot the exact same OUT file in FFT analysis.

Any idea what might have caused this? And how to solve this problem?

[Rob]

When you restart are you opening case and data? Monitors will write out, but if you're using Workbench you may be trying to start from iteration 0 again.

[Danielgkh]

HI I opened my simulation by choosing the "edit" option under "Solution" under FLUENT in Workbench. Then FLUENT open as usual and read all the necessary case and data file.
Everything else was read properly, even the residual chart, but the report plot files.
Now I am wondering, will deleting the cleanup file cause this?

[Danielgkh]

So here are some screenshots.
As you can see here, the correct case & data file has been read, residual chart is also displayed properly.
However, when I wanna report plot, I am unable to do so.
Although I am pretty sure the data is still there, as I am able to plot it in FFT.

[Amine Ben Hadj Ali]

Does it work if you at least for one more iteration/ time step.

[Danielgkh]

no, it does not. When I try to continue running the simulation, the message "OK to overwrite?" will appear.
If I press yes, it will overwrite all the profile file and start simulating from previous time step, without any data from previous time step, other than the residual chart.
If I press no, it will just end the calculation automatically.
I have also found out that one of my other simulation also has this problem.

[dnautiyal]

Please resart workbench

[Danielgkh]

what do you mean exactly by restarting workbench? I had restarted my PC and the same problem always occur.
However this problem does not happen to all of my simulation. For example, I have now 3 separate simulation with the exact same setting but slightly different geometry. The first one display all the result properly, but the 2nd and 3rd ones are having problem.

[Rob]

It's the Fluent interaction with Workbench, it can't write the second out file as it does in standalone mode. Either copy the out file somewhere safe (renaming might work) or run Fluent outside of Workbench. WB tends to assume that we start & run a model to completion in one go, the backend workflow doesn't understand re-starts and blocks Fluent from appending or altering the out file name.

[Danielgkh]

so I had open Fluent in standalone mode and read the case & data file, but the same problem still exists.
So I tried saving a copy of the OUT file into a sub folder and also renaming the OUT file in the same folder, then changing the file path for both separate cases in "Report Files". Is this what you meant by "copy the out file somewhere safe (renaming might work)"? However I still could not plot the chart in both cases.
If what you said about Workbench is true, then does that mean that one need to finish all post processing right after completion? As WB would not display all previous result during relaunch of the application, even if they just want to check the result . I find this quite impossible.
Anyway, I feel like I couldn't do much at this point but to rerun the whole simulation. For future reference, what is actually the best practices in making sure such problem wont happen again, if I wanna continue using Workbench?

[Rob]

OK, I've tested this in 2021R2 and regularly use standalone in 4-5 versions so it sounds like you're doing something to confuse the reports.
Run the workflow through, monitors are saved to (for example) 500 iterations. Save Fluent and WB and shut it down. Reopen WB and open Fluent from the Solution box. Model runs on for another 500 iterations. Checking the monitor using a text editor from the folder and I can see all 1000 data points.
Can you confirm that you are saving Fluent and WB before you close it. Also that you are then reopening on the same machine from the Solution box?

[Danielgkh]

yes, I can confirm that. Before I close Fluent, I always use "save project" in Fluent to save, then for making sure, I will go WB and save project again. Then as backup, I also save it as another backup file. After all this, then only I will close the Fluent windows and WB. I am also reopening the project from the same machine, maybe sometimes connected to different network, but that is all.
Attached are screenshot of the files under Fluent and also the data points in my OUT file. Everything do seems fine.

[Rob]

Not sure, it's working here (on a remote PC) in steady state and transient.

[Danielgkh]

I never have this problem in steady state. Only in transient state.
It seems like this problem happens very seldom, but somehow happens to me 2 out of 3 simulation.
Can you maybe give me some tips or advice on how to best save solution data?

[Rob]

I just set up the model and ran it. Make sure you don't change settings too often (this is due to the WB workflow) and choose the option to use any changes for all models. Otherwise I didn't do anything odd in the set up. Note, I have no parameters in the set up.
Why do you need Workbench?

[Danielgkh]

By setting, do you mean solver setting or WB setting? I changed my solver setting quite often, for example, urf and coupling method, otherwise, I never touch any setting for WB.
I just ran the simulation again and I feel like the problem lies with me interrupting the calculation and save the project halfway for my last 2 simulation. My latest simulation has no problem plotting all the data point when I ran the whole calculation to the end. This was the case for my fist simulation as well.
Usage of WB is not compulsory for me, I just feel like the workflow is smoother with WB. I can actually straight away import the geometry from SpaceClaim into Fluent Meshing then into Fluent Solution.

[Amine Ben Hadj Ali]

WB asks whenever you change something if the settings should be used for this run only or for all calculations.
Always modify settings in the setup cell not in the solution cells.
Best to start from a dummy small example which you can experiment with it.

If you want / plan to interrupt your run several times I recommend running with Fluent Standalone: Meshing and Solver.

[Danielgkh]

Thanks for your tips.
I always choose change setting for all calculations so no issue with this. However, I had always did the wrong thing by changing setting from solution cell when re-running simulation for more time step. Will take note of this.
With this, I think there should be no problem with my data plotting in the future. Thank you so much for your help.

[Rob]

If you open SpaceClaim in standalone mode look for the "Fluent" icon in one of the menus - that takes you straight to Fluent Meshing as you'd see in Workbench, you then transfer to solver when done. We currently teach this as the workflow in the Intro training too. Either approach is good, it's just one or other tends to be marginally better depending on what you're doing: messing with settings is favoured by standalone mode.