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binData in forces functionObject

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Old   November 6, 2019, 10:09
Default binData in forces functionObject
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David Andersson
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Hi,

I am writing my own functionObject and since I am quite new to OpenFOAM i started off by making a copy of the standard functionObject forces and I am now about to adopt it to my needs.

I have managed to understand quite a bit of what is going on in there but on thing that I still don't understand is the binData, that is referred on many places in the code.

For example:

Code:
case BINS_FILE:
        {
            // bin data

            writeHeader(file(i), "Force bins");
            writeHeaderValue(file(i), "bins", nBin_);
            writeHeaderValue(file(i), "start", binMin_);
            writeHeaderValue(file(i), "delta", binDx_);
            writeHeaderValue(file(i), "direction", binDir_);

            vectorField binPoints(nBin_);
            writeCommented(file(i), "x co-ords  :");
            forAll(binPoints, pointi)
            {
                binPoints[pointi] = (binMin_ + (pointi + 1)*binDx_)*binDir_;
                file(i) << tab << binPoints[pointi].x();
            }
            file(i) << nl;

            writeCommented(file(i), "y co-ords  :");
            forAll(binPoints, pointi)
            {
                file(i) << tab << binPoints[pointi].y();
            }
            file(i) << nl;

            writeCommented(file(i), "z co-ords  :");
            forAll(binPoints, pointi)
            {
                file(i) << tab << binPoints[pointi].z();
            }
            file(i) << nl;

            writeCommented(file(i), "Time");

            const word binForceTypes("[pressure,viscous]");
            for (label j = 0; j < nBin_; j++)
            {
                const word jn('(' + Foam::name(j) + ')');
                const word f("forces" + jn + binForceTypes);

                file(i)<< tab << f;
            }
            if (localSystem_)
            {
                for (label j = 0; j < nBin_; j++)
                {
                    const word jn('(' + Foam::name(j) + ')');
                    const word f("localMoments" + jn + binForceTypes);

                    file(i)<< tab << f;
                }
            }

            break;
        }
I more or less understand what this section is doing but I don't understand what the BINS_FILE is.

Thankful for any explanation on this.

Cheers,
David
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Old   February 27, 2020, 17:25
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Gang Wang
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Hi!

I also felt confused about this, do you have any idea about bindata?

Best regards,
Gang
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Old   February 29, 2020, 11:26
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It's writing out a file of the binned data.
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Old   March 2, 2020, 04:52
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Quote:
Originally Posted by me3840 View Post
It's writing out a file of the binned data.
Yes, well that is clear. But what is the "binned data"?
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Old   March 2, 2020, 06:05
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Hosein
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Hii there,

well if you read the description it says the following :

"Member function forces::write() calculates the forces/moments and
writes the forces/moments into the file \<timeDir\>/forces.dat and bin
data (if selected) to the file \<timeDir\>/forces_bin.dat"

also later it follows with the usage of it as :

"Bin data is optional, but if the dictionary is present, the entries must
be defined according o
\table
nBin | number of data bins | yes |
direction | direction along which bins are defined | yes |
cumulative | bin data accumulated with increasing distance | yes |
\endtable"

It is an optional feature and it seems that you may use it when you want to have spatial distribution of forces/moments along a certain direction ... You may try it out to see how it works...
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Old   March 2, 2020, 19:03
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In other words this will get you a distribution of forces along a direction.

This is typical for aero cases where one is interested in seeing where drag or lift has the largest increase or decrease, allowing focused development of that area.
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Old   March 3, 2020, 02:43
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David Andersson
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Quote:
Originally Posted by me3840 View Post
In other words this will get you a distribution of forces along a direction.

This is typical for aero cases where one is interested in seeing where drag or lift has the largest increase or decrease, allowing focused development of that area.
Alright, now I have a better idea of what it does. Thank you for your help!
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