[PeterShi]

Dear Foamers,

I am doing large-eddy simulations (LES), and I am able to get mean pressure from OpenFOAM like this:

p
{
mean on;
prime2Mean on;
base time;
}

I am just curious about how exactly OpenFOAM calculates the mean pressure?

Thank you in advance.

Best,
Peter

[Siassei]

Hello,

look to https://github.com/OpenFOAM/OpenFOAM...fieldAverage.H

mean: arithmetic mean
....
{
mean on;
prime2Mean on;
base time; // iteration
window 200; // optional averaging window
windowName w1; // optional window name (default = "")
}
....

[PeterShi]

Originally Posted by Siassei

Hello,

look to https://github.com/OpenFOAM/OpenFOAM...fieldAverage.H

mean: arithmetic mean
....
{
mean on;
prime2Mean on;
base time; // iteration
window 200; // optional averaging window
windowName w1; // optional window name (default = "")
}
....

Hi Siassei,

Thank you for your response, and I read the code that you provided.

Just want to double check:
1. In the sub-dictionary window, we assign the period of time over which the pressure is averaged?
2. What are available options for windowName? What does w1 mean? (I know what is the window and why we need to use it)

Thank you!

Best,
Peter

[Siassei]

Originally Posted by PeterShi

1. In the sub-dictionary window, we assign the period of time over which the pressure is averaged?

Fields are entered as a list of sub-dictionaries, which indicate the type of
averages to perform, and can be updated during the calculation. The current
options include:
- \c mean: arithmetic mean
- \c prime2Mean: prime-squared mean
- \c base: average over 'time', or 'iteration'
- \c window: optional averaging window, specified in 'base' units

Originally Posted by PeterShi

2. What are available options for windowName? What does w1 mean? (I know what is the window and why we need to use it)

I'm not sure, but I think the windowName is for purpose only. Perhaps if you writing advanced code, it could be usefull for debuging case.

[PeterShi]

Originally Posted by Siassei

Fields are entered as a list of sub-dictionaries, which indicate the type of
averages to perform, and can be updated during the calculation. The current
options include:
- \c mean: arithmetic mean
- \c prime2Mean: prime-squared mean
- \c base: average over 'time', or 'iteration'
- \c window: optional averaging window, specified in 'base' units


I'm not sure, but I think the windowName is for purpose only. Perhaps if you writing advanced code, it could be usefull for debuging case.

I see. So we can either average over time or iterations.

I do not think it is for debugging purpose only. I know there are a couple of window functions, like Hanning window, Flat Top window, etc. I feel like windowName should correspond to those functions.

[Siassei]

Interessting

The averaging window corresponds to the averaging interval (iters or time)
If not specified, the averaging is over 'all iters/time'

from https://cpp.openfoam.org/v6/fieldAve...ce.html#l00217