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========= |
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\\ / O peration | Website: https://openfoam.org
\\ / A nd | Copyright (C) 2023-2026 OpenFOAM Foundation
\\/ M anipulation |
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License
This file is part of OpenFOAM.
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under the terms of the GNU General Public License as published by
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Class
Foam::PiersonMoskowitz
Description
Pierson-Moskowitz wave spectrum. This spectrum has the following form:
\f[
S(\omega) = \frac{\alpha g^2}{\omega^5} \exp \left(- \beta \\
\left( \frac{\omega_0}{\omega} \right)^4 \right)
\f]
\vartable
\omega | angular frequency [rad/s], equal to \f$2 \pi f\f$
f | frequency [Hz]
S(\omega) | spectral density [m^2/Hz]
\alpha | coefficient, equal to 8.1e3
\beta | coefficient, equal to 0.74
\omega_0 | reference angular frequency, equal to \f$g/U_{19.5}\f$
U_{19.5} | reference velocity magnitude, 19.5 metres above the sea \\
surface
\endvartable
References:
\verbatim
Pierson Jr, W. J., & Moskowitz, L. (1964).
A proposed spectral form for fully developed wind seas based on the \\
similarity theory of SA Kitaigorodskii.
Journal of geophysical research, 69(24), 5181-5190.
\endverbatim
\verbatim
Stewart, R. H. (2008).
Introduction to physical oceanography.
Robert H. Stewart.
\endverbatim
Usage
\table
Property | Description | Required? | Default
U19_5 | The air speed 19.5 metres above the \\
surface [m/s] | yes |
\endtable
Example specification:
\verbatim
spectrum PiersonMoskowitz;
PiersonMoskowitz
{
U19_5 15;
}
\endverbatim
SourceFiles
PiersonMoskowitz.C
\*---------------------------------------------------------------------------*/
#ifndef PiersonMoskowitz_H
#define PiersonMoskowitz_H
#include "waveSpectrum.H"
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
namespace Foam
{
namespace waveSpectra
{
/*---------------------------------------------------------------------------*\
Class PiersonMoskowitz Declaration
\*---------------------------------------------------------------------------*/
class PiersonMoskowitz
:
public waveSpectrum
{
// Private Data
//- Reference velocity magnitude
const scalar U19_5_;
//- Alpha coefficient
const scalar alpha_;
//- Beta coefficient
const scalar beta_;
public:
//- Runtime type information
TypeName("PiersonMoskowitz");
// Constructors
//- Construct a copy
PiersonMoskowitz(const PiersonMoskowitz& spectrum);
//- Construct from a dictionary and gravity
PiersonMoskowitz(const dictionary& dict, const scalar g);
//- Construct a clone
virtual autoPtr<waveSpectrum> clone() const
{
return autoPtr<waveSpectrum>(new PiersonMoskowitz(*this));
}
//- Destructor
virtual ~PiersonMoskowitz();
// Member Functions
//- Evaluate the wave spectral density at the given frequencies [m^2/Hz]
virtual tmp<scalarField> S(const scalarField& f) const;
//- Evaluate the integral of the wave spectral density at the given
// frequencies [m^2]
virtual tmp<scalarField> integralS(const scalarField& f) const;
//- Return the frequency below which a given fraction of the spectrum's
// total power falls []
virtual scalar fFraction(const scalar fraction) const;
//- Write
virtual void write(Ostream& os) const;
};
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
} // End namespace waveSpectra
} // End namespace Foam
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
#endif
// ************************************************************************* //
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