[m.uzair]

Hi everyone,

I want to get the time averaged (say ~15s average) of the variables like velocity profiles, temperature, mass flow at a cross-section of the geometry.

In my (transient case) simulations, the real flow time is 10 seconds. I enabled data sampling for time statistics in fluent from 0 seconds. So, I am getting time averaged values of lets say velocity magnitude from 0 to 10 s. But I want time-averaged values from 5 to 10 seconds. I saved case and data files every 100 time steps.

I need to find the "average solution" for the past "n" timesteps from the data files that have already been saved.
Is there any method to get those time-averaged values between specific intervals of time?

Let me explain a bit more. The user has iterated the case till time step no. 20000, saving files after every 100 time steps. Now the user wants to see the average solution for time steps 500 to 1200. Is there a way to load the appropriate data files (for these intervals of time), call a UDF to find the averages of variables?
Thank you in advance.

[LuckyTran]

The algebra is simple. The implementation is tricky.

(N1 + N2)*Final_Avg = N1*1st_Avg +N2*2nd_Avg

And you want to find the 2nd_Avg

One way is to use custom field functions and set them equal to the mean variables at time-step 100. Then write an interpolate file which you can then read into the simulation at time-step 20 000 or whatever. Then again using custom field functions, you can then do the calculation to remove the 1st average. This is not so bad to do manually if you only have a few variables, but if you have a lot, then it needs to be done with a journal.

[m.uzair]

Originally Posted by LuckyTran

The algebra is simple. The implementation is tricky.

(N1 + N2)*Final_Avg = N1*1st_Avg +N2*2nd_Avg

And you want to find the 2nd_Avg

One way is to use custom field functions and set them equal to the mean variables at time-step 100. Then write an interpolate file which you can then read into the simulation at time-step 20 000 or whatever. Then again using custom field functions, you can then do the calculation to remove the 1st average. This is not so bad to do manually if you only have a few variables, but if you have a lot, then it needs to be done with a journal.

Dear, Thanx for your advice.
How can I do it with the journal file, writing data of a lot of time steps to a file. Can you explain it a bit more comprehensively. I am new to this.
Thanks again

[LuckyTran]

Originally Posted by m.uzair

Dear, Thanx for your advice.
How can I do it with the journal file, writing data of a lot of time steps to a file. Can you explain it a bit more comprehensively. I am new to this.
Thanks again

Learn how to do it manually using only TUI (i.e. the text commands). Then simply put these text into a text file.

If this is too complicated, it might be faster just to re-run the simulation and average over the correct window.

[m.uzair]

Originally Posted by LuckyTran

The algebra is simple. The implementation is tricky.

(N1 + N2)*Final_Avg = N1*1st_Avg +N2*2nd_Avg

And you want to find the 2nd_Avg

One way is to use custom field functions and set them equal to the mean variables at time-step 100. Then write an interpolate file which you can then read into the simulation at time-step 20 000 or whatever. Then again using custom field functions, you can then do the calculation to remove the 1st average. This is not so bad to do manually if you only have a few variables, but if you have a lot, then it needs to be done with a journal.

If I take into account first average, it will affect results. I want to exclude first average because the first 5 seconds of my simulation are unsteady.
If I can put instantaneous results into a file and average it, that will work. But I don't know how to do it