noiseFFT.H

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/*---------------------------------------------------------------------------*\
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    Copyright (C) 2011-2015 OpenFOAM Foundation
    Copyright (C) 2016-2017 OpenCFD Ltd.
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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.
 
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    for more details.
 
    You should have received a copy of the GNU General Public License
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Class
    Foam::noiseFFT
 
Description
    Performs FFT of pressure field to generate noise data.
 
    General functionality:
    - Pf: fft of the pressure data
    - meanPf: multi-window mean fft
    - RMSmeanPf: multi-window RMS mean fft
    - PSDf: multi-window power spectral density (PSD) in frequency domain
    - PSD: power spectral density in dB/Hz
    - SPL: sound pressure level in dB
 
    Octave-based data:
    - PSD spectrum
    - SPL spectrum
 
SourceFiles
    noiseFFT.C
 
SeeAlso
    windowModel.H
 
\*---------------------------------------------------------------------------*/
 
#ifndef noiseFFT_H
#define noiseFFT_H
 
#include "scalarField.H"
#include "graph.H"
#include "windowModel.H"
#include <fftw3.h>
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                          Class noiseFFT Declaration
\*---------------------------------------------------------------------------*/
 
class noiseFFT
:
    public scalarField
{
    //- FFTW planner information.
    //  Storage as double for use directly with FFTW.
    struct planInfo
    {
        bool active;
        label windowSize;
        List<double> in;
        List<double> out;
        fftw_plan plan;
    };
 
    //- Octave band information
    struct octaveBandInfo
    {
        label octave;
 
        // IDs of bin boundaries in pressure data
        labelList binIDs;
 
        // Centre frequencies for each bin
        scalarField centreFreq;
    };
 
 
    // Private data
 
        //- Time spacing of the raw data (uniform)
        scalar deltaT_;
 
        //- Plan information for FFTW
        mutable planInfo planInfo_;
 
 
public:
 
    //- Reference pressure
    static scalar p0;
 
    //- Construct from pressure field
    noiseFFT(const scalar deltaT, const label windowSize = -1);
 
    //- Destructor. Cleanup/destroy plan
    ~noiseFFT();
 
 
    // Member Functions
 
        //- Return the FFT frequencies
        static tmp<scalarField> frequencies
        (
            const label N,
            const scalar deltaT
        );
 
        //- Return the PSD [dB/Hz]
        //  Input PSD in [Pa^2/Hz]
        static tmp<scalarField> PSD(const scalarField& PSDf);
 
        //- Return the SPL [dB]
        //  Input P(rms)^2 in [Pa^2]
        static tmp<scalarField> SPL(const scalarField& Prms2);
 
        //- Return a list of the frequency indices wrt f field that
        //  correspond to the bands limits for a given octave
        static void octaveBandInfo
        (
            const scalarField& f,
            const scalar fLower,
            const scalar fUpper,
            const scalar octave,
            labelList& fBandIDs,
            scalarField& fCentre
        );
 
        //- Set the pressure data
        //- \note transfers storage to *this
        void setData(scalarList& data);
 
        //- Set the pressure data by reading from file with an optional offset
        void setData(const fileName& pFileName, const label skip = 0);
 
 
        //- Return the graph of pressure as a function of time
        graph pt() const;
 
        //- Return the fft of the given pressure data
        tmp<scalarField> Pf(const tmp<scalarField>& pn) const;
 
        //- Return the multi-window mean fft of the complete pressure data [Pa]
        graph meanPf(const windowModel& window) const;
 
        //- Return the multi-window RMS mean fft of the complete pressure
        //  data [Pa]
        graph RMSmeanPf(const windowModel& window) const;
 
        //- Return the multi-window PSD (power spectral density) of the complete
        //  pressure data [Pa^2/Hz]
        graph PSDf(const windowModel& window) const;
 
        //- Return the PSD [dB/Hz]
        //  Takes PSD in [Pa^2/Hz]
        graph PSD(const graph& gPSDf) const;
 
        //- Generate octave data
        graph octaves
        (
            const graph& g,
            const labelUList& freqBandIDs
        ) const;
 
        //- Convert the db into Pa
        scalar dbToPa(const scalar db) const;
 
        //- Convert the db-field into Pa
        tmp<scalarField> dbToPa(const tmp<scalarField>& db) const;
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //