[lukas.lebo]

Hello

I'm trying to make an utility that can calculate the mean and prime2mean of the pressure coefficient cp. My simulations already create the fields for pMean and pPrime2Mean during runtime.

I basically want to do this calculation:
cp = p/(0.5*U_ref^2)

where U_ref should be my reference velocity. Here I'd like to take the area averaged velocity from the inlet (patch is actually named "inlet").

How do I get a (scalar) value that is the area average of the inlet velocity?

And can I define my own variable? i.e. "double u_ref = ...;"

Thanks so much!



PS: I took another utility and modified it. You can take a look here:

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2011-2012 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

Application
    cpMean

Description
    Calculates and writes some mean fields from an LES calculation. The
    following fields are created:
        - cpMean: mean pressure coefficient
        - cpPrime2Mean: variance of the pressure coefficient
    Fields UMean, pPrime2Mean and pMean must exist.

\*---------------------------------------------------------------------------*/

#include "calc.H"
#include "fvc.H"
#include "fvCFD.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

void Foam::calc(const argList& args, const Time& runTime, const fvMesh& mesh)
{
    IOobject pMeanHeader
    (
        "pMean",
        runTime.timeName(),
        mesh,
        IOobject::MUST_READ
    );


    IOobject pPrime2MeanHeader
    (
        "pPrime2Mean",
        runTime.timeName(),
        mesh,
        IOobject::MUST_READ
    );


    IOobject UMeanHeader
    (
        "UMean",
        runTime.timeName(),
        mesh,
        IOobject::MUST_READ
    );
    
  
    if
    (
        pMeanHeader.headerOk()
     && pPrime2MeanHeader.headerOk()
     && UMeanHeader.headerOk()
    )
    {
        Info<< "    Reading average field pMean" << endl;
        const volScalarField pMean(pMeanHeader, mesh);

        Info<< "    Reading average field pPrime2Mean" << endl;
        const volScalarField pPrime2Mean(pPrim2MeanHeader, mesh);

        Info<< "    Reading average field UMean" << endl;
        const volVectorField UMean(UMeanHeader, mesh);


        volScalarField cpMean
        (
            IOobject
            (
                "cpMean",
                runTime.timeName(),
                mesh,
                IOobject::NO_READ,
                IOobject::AUTO_WRITE
            ),
            mesh,
            dimensionedScalar("dimless",dimless,0)
        );


        volScalarField cpPrime2Mean
        (
            IOobject
            (
                "cpPrime2Mean",
                runTime.timeName(),
                mesh,
                IOobject::NO_READ,
                IOobject::AUTO_WRITE
            ),
            mesh,
            dimensionedScalar("dimless",dimless,0)
        );

        // double u_ref = ... ; // is this allowed?

        Info<< "    Calculating cpMean" << endl;
	forAll(cpMean,i){
            cpMean[i] = pMean[i]/(0.5*...); // <-- Missing mean velocity at Inlet !!!
	}

        Info<< "    Calculating cpPrime2Mean" << endl;
	forAll(cpPrime2Mean,i){
	    cpPrime2Mean[i] = pPrime2Mean[i]/(0.5*...): // <-- Missing mean velocity at Inlet !!!
	}

        cpMean.write();
	cpPrime2Mean.write();
    }
    else
    {
        Info << "    No pPrime2Mean and/or pMean and/or UMean." << endl;
    }
    
    Info<< "End" << endl;
}


// ************************************************************************* //

[sisetrun]

Hey,
maybe the code from the patchIntegrate tool can help you:

Description
Calculates the integral of the specified field over the specified patch.

https://github.com/OpenFOAM/OpenFOAM...tchIntegrate.C