atmosphere.cpp

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#include "atmosphere.h"
#include "embedded_memory.h"
 
static ROM struct
{
    float range1Begin = 223.15f;
    float range2Begin = 273.16f;
    float rangeEnd = 333.15f;
    float s[2][6] =
        {
        { 24.8925f, 2.6766f, 0.1327f, 0.0040f, 8.1294e-5f, 1.1624e-6f },
        { 3.3640e3f, 198.8920f, 5.1247f, 0.0741f, 6.364e-4f, 3.0197e-6f }
        };
    float a[2] = { 239.15f, 299.15f };
} PWS;
 
#define POT_2(x)        ((x)*(x))
#define POT_3(x)        ((x)*(x)*(x))
#define POT_4(x)        ((x)*(x)*(x)*(x))
#define POT_5(x)        ((x)*(x)*(x)*(x)*(x))
 
float atmosphere_t::calculateSaturationVaporPressure(float temp)
{
    if (PWS.range1Begin <= temp && temp < PWS.range2Begin)
      {
        return (PWS.s[0][0] + PWS.s[0][1] * ((temp - PWS.a[0]))
                + PWS.s[0][2] * POT_2((temp - PWS.a[0]))
                + PWS.s[0][3] * POT_3((temp - PWS.a[0]))
                + PWS.s[0][4] * POT_4((temp - PWS.a[0]))
                + PWS.s[0][5] * POT_5((temp - PWS.a[0])));
      }
    else if (PWS.range2Begin <= temp && temp <= PWS.rangeEnd)
      {
        return (PWS.s[1][0] + PWS.s[1][1] * ((temp - PWS.a[1]))
                + PWS.s[1][2] * POT_2((temp - PWS.a[1]))
                + PWS.s[1][3] * POT_3((temp - PWS.a[1]))
                + PWS.s[1][4] * POT_4((temp - PWS.a[1]))
                + PWS.s[1][5] * POT_5((temp - PWS.a[1])));
      }
    return 0.0f;
}
 
float atmosphere_t::calculateGasConstantHumAir(
    float humidity, float pressure, float temperature)
{
    float satVapPressure = calculateSaturationVaporPressure(temperature);
    float var1 =
        humidity * satVapPressure / pressure * ONE_MINUS_RATIO_GAS_CONSTANTS;
 
    return (GAS_CONST_DRY_AIR / (1 - var1));
}
 
float atmosphere_t::calculateAirDensity(
    float humidity, float pressure, float temperature)
{
    float abs_temp = (CELSIUS_TO_KELVIN_OFFSET + temperature);
    float gasConst = calculateGasConstantHumAir(humidity, pressure, abs_temp);
    return pressure / gasConst / temperature;
}