log.H

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/*---------------------------------------------------------------------------*\
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-------------------------------------------------------------------------------
    Copyright (C) 2018-2019 OpenFOAM Foundation
    Copyright (C) 2020 OpenCFD Ltd.
-------------------------------------------------------------------------------
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/>.
 
Class
    Foam::functionObjects::log
 
Group
    grpFieldFunctionObjects
 
Description
    Computes the natural logarithm of an input \c volScalarField.
 
    \f[
        f = s \ln(max(f_0, a)) + t
    \f]
 
    where
    \vartable
      f     | Output volScalarField
      f_0   | Input volScalarField
      \ln   | Natural logarithm operator
      a     | Clip scalar
      s     | Scaling factor
      t     | Offset factor
    \endvartable
 
    \table
      Operand       | Type           | Location
      input         | volScalarField | $FOAM_CASE/<time>/<inpField>
      output file   | -              | -
      output field  | volScalarField | $FOAM_CASE/<time>/<outField>
    \endtable
 
Usage
    Minimal example by using \c system/controlDict.functions:
    \verbatim
    log1
    {
        // Mandatory entries (unmodifiable)
        type            log;
        libs            (fieldFunctionObjects);
 
        // Mandatory (inherited) entry (runtime modifiable)
        field           <inpField>;
 
        // Optional entries (runtime modifiable)
        clip            1e-3;
        checkDimensions false;
        scale           1.0;
        offset          0.0;
 
        // Optional (inherited) entries
        ...
    }
    \endverbatim
 
    where the entries mean:
    \table
      Property     | Description                        | Type | Req'd | Dflt
      type         | Type name: log                     | word |  yes  | -
      libs         | Library name: fieldFunctionObjects | word |  yes  | -
      field        | Name of the operand field          | word |  yes  | -
      clip         | Value to clip the operand field values <!--
                 --> to prevent zero or negative input  | scalar | no  | SMALL
      checkDimensions | Flag to check dimensions of the operand field <!--
                                                    --> | bool   | no  | true
      scale        | Scaling factor - \c s above        | scalar | no  | 1.0
      offset       | Offset factor - \c t above         | scalar | no  | 0.0
    \endtable
 
    The inherited entries are elaborated in:
     - \link functionObject.H \endlink
     - \link fieldExpression.H \endlink
 
    Minimal example by using the \c postProcess utility:
    \verbatim
        postProcess -func "log(<inpField>)" -scale 1.0 -offset 0.0
    \endverbatim
 
Note
    - Performs \f$\ln(max(x, a))\f$ where \f$x\f$ is a \c volScalarField, and
    \f$a\f$ a clip scalar, equals to \c SMALL by default. This prevents zero or
    negative input \f$x\f$, hence the domain error in the natural logarithm.
    - Dimension checking can optionally be suspended if \f$x\f$ is dimensioned.
 
See also
    - Foam::functionObject
    - Foam::functionObjects::fieldExpression
    - Foam::functionObjects::fvMeshFunctionObject
    - ExtendedCodeGuide::functionObjects::field::log
 
SourceFiles
    log.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef functionObjects_log_H
#define functionObjects_log_H
 
#include "fieldExpression.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
namespace functionObjects
{
 
/*---------------------------------------------------------------------------*\
                          Class log Declaration
\*---------------------------------------------------------------------------*/
 
class log
:
    public fieldExpression
{
    // Private Data
 
        //- Flag to check dimensions of the operand
        Switch checkDimensions_;
 
        //- Value to clip the operand field values
        //- to prevent zero or negative input
        scalar clipValue_;
 
        //- Scaling factor
        scalar scale_;
 
        //- Offset factor
        scalar offset_;
 
 
    // Private Member Functions
 
        //- Calculate the log field and return true if successful
        virtual bool calc();
 
 
public:
 
    //- Runtime type information
    TypeName("log");
 
 
    // Constructors
 
        //- Construct from Time and dictionary
        log
        (
            const word& name,
            const Time& runTime,
            const dictionary& dict
        );
 
        //- No copy construct
        log(const log&) = delete;
 
        //- No copy assignment
        void operator=(const log&) = delete;
 
 
    //- Destructor
    virtual ~log() = default;
 
 
    // Member Functions
 
        //- Read the randomise data
        virtual bool read(const dictionary&);
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace functionObjects
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //