atmospheric_conditions.cpp

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#include <math.h>
 
#include "Tympan/models/common/atmospheric_conditions.h"
 
#ifndef M_PI
    #define M_PI 3.1415926535897932384626433832795
#endif
 
const double AtmosphericConditions::Z_ref = 400.0;
const double AtmosphericConditions::reference_pressure = 101325.0;
const double AtmosphericConditions::reference_temperature = 293.15;
const double AtmosphericConditions::absolute_zero = 273.15;
 
AtmosphericConditions::AtmosphericConditions(double static_pressure_, double temperature_, double hygrometry_)
    : static_pressure(static_pressure_), temperature(temperature_), hygrometry(hygrometry_)
{
    compute_k();
    compute_absorption_spectrum();
    compute_absorption_spectrum_oct();
}
 
void AtmosphericConditions::compute_absorption_spectrum()
{
    double f2 = NAN;                                 // Carre de la frequence de travail
    double tA_classic = NAN, tA_N = NAN, tA_O = NAN; // Termes d'absoption classique, Azote Oxygene
 
    const double tK = temperature + absolute_zero;              // temperature absolue exprimee en Kelvin
    const double pr_rel = static_pressure / reference_pressure; // Pression relative
    const double t_rel = tK / reference_temperature;            // Temperature relative
 
    const double h_molaire = compute_hm();
 
    // Frequences de relaxation de l'oxygene (frO) et de l'azote (frN)
    const double frO =
        pr_rel * (24.0 + (4.04 * 10000.0 * h_molaire * ((0.02 + h_molaire) / (0.391 + h_molaire))));
    const double frN = pr_rel * pow(t_rel, -0.5) *
                       (9.0 + 280.0 * h_molaire * exp((-4.170 * (pow(t_rel, (-1.0 / 3.0)) - 1))));
 
    OTabFreq tabFreq = OSpectre::getTabFreqExact();
 
    for (unsigned int i = 0; i < absorption_spectrum.getNbValues(); i++)
    {
        f2 = tabFreq[i] * tabFreq[i];
 
        tA_classic = 1.84e-11 * (1.0 / pr_rel) * sqrt(t_rel);
        tA_O = 0.01275 * exp(-2239.1 / tK) * (1.0 / (frO + (f2 / frO)));
        tA_N = 0.1068 * exp(-3352.0 / tK) * (1.0 / (frN + (f2 / frN)));
 
        absorption_spectrum.getTabValReel()[i] =
            (8.686 * f2 * (tA_classic + (pow(t_rel, -2.5) * (tA_O + tA_N))));
    }
}
 
void AtmosphericConditions::compute_absorption_spectrum_oct()
{
    absorption_spectrum_oct.setType(SPECTRE_TYPE_ABSO); // Absorption spectrum
    unsigned int indiceDepart = 2;
    unsigned int indice = 0;
    for (unsigned int i = indiceDepart; i < TY_SPECTRE_DEFAULT_NB_ELMT - 2; i += 3, indice++)
    {
        absorption_spectrum_oct.getTabValReel()[indice] =
            round(absorption_spectrum.getTabValReel()[i + 1] * 10000) /
            10; // Express absorption coefficient in dB per km round to one decimal place
    }
}
 
double AtmosphericConditions::compute_c() const
{
    const double gamma = 1.41;
    const double R = 8.31441;
    const double M = 0.029;
    const double tK = temperature + absolute_zero;
 
    return sqrt((gamma * R * tK) / M);
}
 
double AtmosphericConditions::compute_z()
{
    const double R = 8.31441; // Constante des gazs parfaits
    const double tK = temperature + absolute_zero;
    const double M = 0.029; // Masse molaire de l'air
 
    return (M * (static_pressure / (R * tK))) * compute_c();
}
 
void AtmosphericConditions::compute_k()
{
    double soundSpeed = compute_c();
    OTabFreq tabFreq = OSpectre::getTabFreqExact();
 
    for (unsigned int i = 0; i < tabFreq.size(); i++)
    {
        wave_number.getTabValReel()[i] = (2 * M_PI * tabFreq[i]) / soundSpeed;
    }
}
 
double AtmosphericConditions::compute_hm() const
{
    double T01 = absolute_zero + 0.01;                    // Temperature isotherme au point triple
    double tK = temperature + absolute_zero;              // Temperature en Kelvin
    double pr_rel = static_pressure / reference_pressure; // Pression relative
 
    double C = -6.8346 * pow((T01 / tK), 1.261) + 4.6151;
 
    double prSat_prRef = pow(10, C);
 
    return hygrometry * prSat_prRef * pr_rel;
}
 
OSpectre AtmosphericConditions::compute_length_absorption(double length) const
{
    return absorption_spectrum.mult(-(length / 2.0)).toGPhy();
}
 
OSpectreOctave AtmosphericConditions::compute_length_absorption_oct(double length) const
{
    return absorption_spectrum_oct * (length / 1000.0);
}