forces.H

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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
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    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/>.

Class
    Foam::functionObjects::forces

Description
    Calculates the forces and moments by integrating the pressure and
    skin-friction forces over a given list of patches.

    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

    Example of function object specification:
    \verbatim
    forces1
    {
        type        forces;
        libs        ("libforces.so");
        ...
        log         yes;
        patches     (walls);

        binData
        {
            nBin        20;
            direction   (1 0 0);
            cumulative  yes;
        }
    }
    \endverbatim

Usage
    \table
        Property     | Description             | Required    | Default value
        type         | Type name: forces       | yes         |
        log          | Write force data to standard output | no | no
        patches      | Patches included in the forces calculation | yes |
        p            | Pressure field name     | no          | p
        U            | Velocity field name     | no          | U
        rho          | Density field name (see below) | no   | rho
        phase        | Phase name for phase-fraction  | no   |
        CofR         | Centre of rotation (see below) | no   |
        directForceDensity | Force density supplied directly (see below)|no|no
        fD           | Name of force density field (see below) | no | fD
    \endtable

    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

  Note
    - For incompressible cases, set \c rho to \c rhoInf and provide
      a \c rhoInf value corresponding to the free-stream constant density.
    - If the \c phase name is specified the corresponding phase-fraction field
      \c alpha.<phase> is used to filter the surface force field
      before integration.
    - If the force density is supplied directly, set the \c directForceDensity
      flag to 'yes', and supply the force density field using the \c
      fDName entry
    - The centre of rotation (CofR) for moment calculations can either be
      specified by an \c CofR entry, or be taken from origin of the local
      coordinate system.  For example,
      \verbatim
          CofR        (0 0 0);
      \endverbatim
      or
      \verbatim
          origin (0 0 0);
          coordinateRotation
          {
              type axesRotation;
              e1 (1 0 0);
              e3 (0 0 1);
          }
      \endverbatim

See also
    Foam::functionObject
    Foam::functionObjects::fvMeshFunctionObject
    Foam::functionObjects::logFiles
    Foam::functionObjects::timeControl
    Foam::forceCoeffs

SourceFiles
    forces.C

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

#ifndef functionObjects_forces_H
#define functionObjects_forces_H

#include "fvMeshFunctionObject.H"
#include "logFiles.H"
#include "coordinateSystem.H"
#include "volFieldsFwd.H"
#include "HashSet.H"

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

namespace Foam
{
namespace functionObjects
{

/*---------------------------------------------------------------------------*\
                           Class forces Declaration
\*---------------------------------------------------------------------------*/

class forces
:
    public fvMeshFunctionObject,
    public logFiles
{

protected:

    // Protected data

        //- Enumeration for ensuring the right file is accessed
        enum class fileID
        {
            mainFile = 0,
            binsFile = 1
        };

        //- Pressure, viscous and porous force per bin
        List<Field<vector>> force_;

        //- Pressure, viscous and porous moment per bin
        List<Field<vector>> moment_;


        // Read from dictionary

            //- Patches to integrate forces over
            labelHashSet patchSet_;

            //- Name of pressure field
            word pName_;

            //- Name of velocity field
            word UName_;

            //- Name of density field (optional)
            word rhoName_;

            //- The name of the phase (optional)
            word phaseName_;

            //- Is the force density being supplied directly?
            Switch directForceDensity_;

            //- The name of the force density (fD) field
            word fDName_;

            //- Reference density needed for incompressible calculations
            scalar rhoRef_;

            //- Reference pressure
            scalar pRef_;

            //- Coordinate system used when evaluating forces/moments
            coordinateSystem coordSys_;

            //- Flag to indicate whether we are using a local co-ordinate sys
            bool localSystem_;

            //- Flag to include porosity effects
            bool porosity_;


            // Bin information

                //- Number of bins
                label nBin_;

                //- Direction used to determine bin orientation
                vector binDir_;

                //- Distance between bin divisions
                scalar binDx_;

                //- Minimum bin bounds
                scalar binMin_;

                //- Bin positions along binDir
                List<point> binPoints_;

                //- Should bin data be cumulative?
                bool binCumulative_;


            //- Initialised flag
            bool initialised_;


    // Protected Member Functions

        using logFiles::file;

        Ostream& file(const fileID fid)
        {
            return logFiles::file(label(fid));
        }

        //- Create file names for forces and bins
        wordList createFileNames(const dictionary& dict) const;

        //- Output file header information
        virtual void writeFileHeader(const label i);

        //- Initialise the fields
        void initialise();

        //- Return the effective viscous stress (laminar + turbulent).
        tmp<volSymmTensorField> devTau() const;

        //- Dynamic viscosity field
        tmp<volScalarField> mu() const;

        //- Return rho if specified otherwise rhoRef
        tmp<volScalarField> rho() const;

        //- Return rhoRef if the pressure field is dynamic, i.e. p/rho
        //  otherwise return 1
        scalar rho(const volScalarField& p) const;

        //- Get the volume fraction field
        tmp<volScalarField> alpha() const;

        //- Get the volume fraction field on a patch
        tmp<scalarField> alpha(const label patchi) const;

        //- Accumulate bin data
        void applyBins
        (
            const vectorField& Md,
            const vectorField& fN,
            const vectorField& fT,
            const vectorField& fP,
            const vectorField& d
        );

        //- Helper function to write force data
        void writeForces();

        //- Helper function to write bin data
        void writeBins();


public:

    //- Runtime type information
    TypeName("forces");


    // Constructors

        //- Construct from Time and dictionary
        forces
        (
            const word& name,
            const Time& runTime,
            const dictionary& dict
        );

        //- Construct from objectRegistry and dictionary
        forces
        (
            const word& name,
            const objectRegistry& obr,
            const dictionary&
        );

        //- Disallow default bitwise copy construction
        forces(const forces&) = delete;


    //- Destructor
    virtual ~forces();


    // Member Functions

        //- Read the forces data
        virtual bool read(const dictionary&);

        //- Return the list of fields required
        virtual wordList fields() const
        {
            return wordList::null();
        }

        //- Calculate the forces and moments
        virtual void calcForcesMoment();

        //- Return the total force
        virtual vector forceEff() const;

        //- Return the total moment
        virtual vector momentEff() const;

        //- Execute, currently does nothing
        virtual bool execute();

        //- Write the forces
        virtual bool write();


    // Member Operators

        //- Disallow default bitwise assignment
        void operator=(const forces&) = delete;
};


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

} // End namespace functionObjects
} // End namespace Foam

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

#endif

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