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Fix AB water vapor pressure calc #4956

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merged 5 commits into from
May 29, 2017
Merged

Fix AB water vapor pressure calc #4956

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efe8c63
Fix AB water vapor pressure calc
PabstMirror Feb 27, 2017
ba427ae
Fix calc in weather
PabstMirror Feb 27, 2017
8873c11
Cleanup usage of constant
PabstMirror Mar 1, 2017
4ec0d67
Merge branch 'master' into fixABHumidity
PabstMirror May 27, 2017
73edbed
Add RVExtensionVersion, Rebuild AB DLLs
PabstMirror May 27, 2017
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2 changes: 1 addition & 1 deletion addons/weather/functions/fnc_calculateAirDensity.sqf
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Expand Up @@ -23,7 +23,7 @@ _pressure = _pressure * 100; // hPa to Pa

if (_relativeHumidity > 0) then {
// Saturation vapor pressure calculated according to: http://wahiduddin.net/calc/density_algorithms.htm
private _pSat = 6.1078 * 10 ^ ((7.5 * _temperature) / (_temperature + 237.3));
private _pSat = 610.78 * 10 ^ ((7.5 * _temperature) / (_temperature + 237.3));
private _vaporPressure = _relativeHumidity * _pSat;
private _partialPressure = _pressure - _vaporPressure;

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2 changes: 1 addition & 1 deletion extensions/advanced_ballistics/AdvancedBallistics.cpp
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Expand Up @@ -94,7 +94,7 @@ double calculateAirDensity(double temperature, double pressure, double relativeH

if (relativeHumidity > 0) {
double _pSat = 6.1078 * pow(10, ((7.5 * temperature) / (temperature + 237.3)));
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Shouldn't 6.1078 (hPa) be converted to Pa directly here instead of converting it in vaporPressure? I find it more clear than later multiplying by 100.0 and having _pSat in hPa while vaporPressure in Pa

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Going to use 610.78 and added note

double vaporPressure = relativeHumidity * _pSat;
double vaporPressure = 100 * relativeHumidity * _pSat;
double partialPressure = pressure - vaporPressure;

return (partialPressure * DRY_AIR_MOLAR_MASS + vaporPressure * WATER_VAPOR_MOLAR_MASS) / (UNIVERSAL_GAS_CONSTANT * KELVIN(temperature));
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