X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FFDM%2FYASim%2FAtmosphere.cpp;h=5fb7347f94f42e8a5ed3472bb6fc1396c675f8b1;hb=d66903e9ad63b91182ccc25d9bb82f18f8dd98b6;hp=0ace3869fa2a3d59ae7776787187a0b879a5de29;hpb=f0e6716953604730579a5e45f785fd063737dce4;p=flightgear.git diff --git a/src/FDM/YASim/Atmosphere.cpp b/src/FDM/YASim/Atmosphere.cpp index 0ace3869f..5fb7347f9 100644 --- a/src/FDM/YASim/Atmosphere.cpp +++ b/src/FDM/YASim/Atmosphere.cpp @@ -7,36 +7,51 @@ namespace yasim { // McCormick lists 299.16/101325/1.22500, but those don't agree with // R=287. I chose to correct the temperature to 288.20, since 79F is // pretty hot for a "standard" atmosphere. +// Numbers above 19000 meters calculated from src/Environment/environment.cxx // meters kelvin Pa kg/m^3 -float Atmosphere::data[][4] = {{ 0, 288.20, 101325, 1.22500 }, - { 900, 282.31, 90971, 1.12260 }, - { 1800, 276.46, 81494, 1.02690 }, - { 2700, 270.62, 72835, 0.93765 }, - { 3600, 264.77, 64939, 0.85445 }, - { 4500, 258.93, 57752, 0.77704 }, - { 5400, 253.09, 51226, 0.70513 }, - { 6300, 247.25, 45311, 0.63845 }, - { 7200, 241.41, 39963, 0.57671 }, - { 8100, 235.58, 35140, 0.51967 }, - { 9000, 229.74, 30800, 0.46706 }, - { 9900, 223.91, 26906, 0.41864 }, - { 10800, 218.08, 23422, 0.37417 }, - { 11700, 216.66, 20335, 0.32699 }, - { 12600, 216.66, 17654, 0.28388 }, - { 13500, 216.66, 15327, 0.24646 }, - { 14400, 216.66, 13308, 0.21399 }, - { 15300, 216.66, 11555, 0.18580 }, - { 16200, 216.66, 10033, 0.16133 }, - { 17100, 216.66, 8712, 0.14009 }, - { 18000, 216.66, 7565, 0.12165 }, - { 18900, 216.66, 6570, 0.10564 }}; +float Atmosphere::data[][4] = {{ -900.0f, 293.91f, 111679.0f, 1.32353f }, + { 0.0f, 288.11f, 101325.0f, 1.22500f }, + { 900.0f, 282.31f, 90971.0f, 1.12260f }, + { 1800.0f, 276.46f, 81494.0f, 1.02690f }, + { 2700.0f, 270.62f, 72835.0f, 0.93765f }, + { 3600.0f, 264.77f, 64939.0f, 0.85445f }, + { 4500.0f, 258.93f, 57752.0f, 0.77704f }, + { 5400.0f, 253.09f, 51226.0f, 0.70513f }, + { 6300.0f, 247.25f, 45311.0f, 0.63845f }, + { 7200.0f, 241.41f, 39963.0f, 0.57671f }, + { 8100.0f, 235.58f, 35140.0f, 0.51967f }, + { 9000.0f, 229.74f, 30800.0f, 0.46706f }, + { 9900.0f, 223.91f, 26906.0f, 0.41864f }, + { 10800.0f, 218.08f, 23422.0f, 0.37417f }, + { 11700.0f, 216.66f, 20335.0f, 0.32699f }, + { 12600.0f, 216.66f, 17654.0f, 0.28388f }, + { 13500.0f, 216.66f, 15327.0f, 0.24646f }, + { 14400.0f, 216.66f, 13308.0f, 0.21399f }, + { 15300.0f, 216.66f, 11555.0f, 0.18580f }, + { 16200.0f, 216.66f, 10033.0f, 0.16133f }, + { 17100.0f, 216.66f, 8712.0f, 0.14009f }, + { 18000.0f, 216.66f, 7565.0f, 0.12165f }, + {18900.0f, 216.66f, 6570.0f, 0.10564f }, + {19812.0f, 216.66f, 5644.0f, 0.09073f }, + {20726.0f, 217.23f, 4884.0f, 0.07831f }, + {21641.0f, 218.39f, 4235.0f, 0.06755f }, + {22555.0f, 219.25f, 3668.0f, 0.05827f }, + {23470.0f, 220.12f, 3182.0f, 0.05035f }, + {24384.0f, 220.98f, 2766.0f, 0.04360f }, + {25298.0f, 221.84f, 2401.0f, 0.03770f }, + {26213.0f, 222.71f, 2087.0f, 0.03265f }, + {27127.0f, 223.86f, 1814.0f, 0.02822f }, + {28042.0f, 224.73f, 1581.0f, 0.02450f }, + {28956.0f, 225.59f, 1368.0f, 0.02112f }, + {29870.0f, 226.45f, 1196.0f, 0.01839f }, + {30785.0f, 227.32f, 1044.0f, 0.01599f }}; // Universal gas constant for air, in SI units. P = R * rho * T. // P in pascals (N/m^2), rho is kg/m^3, T in kelvin. -const float R = 287.1; +const float R = 287.1f; // Specific heat ratio for air, at "low" temperatures. -const float GAMMA = 1.4; +const float GAMMA = 1.4f; float Atmosphere::getStdTemperature(float alt) { @@ -53,10 +68,11 @@ float Atmosphere::getStdDensity(float alt) return getRecord(alt, 3); } -float Atmosphere::calcVEAS(float spd, float pressure, float temp) +float Atmosphere::calcVEAS(float spd, + float pressure, float temp, float density) { static float rho0 = getStdDensity(0); - float densityRatio = calcDensity(pressure, temp) / rho0; + float densityRatio = density / rho0; return spd * Math::sqrt(densityRatio); } @@ -78,8 +94,8 @@ float Atmosphere::calcVCAS(float spd, float pressure, float temp) // (1+(mach^2)/5)^(gamma/(gamma-1)) cp = Math::pow(1+0.2*m2, 3.5); } else { - float tmp0 = ((144/25.) * m2) / (28/5.*m2 - 4/5.); - float tmp1 = ((14/5.) * m2 - (2/5.)) * (5/12.); + float tmp0 = ((144.0f/25.0f) * m2) / (28.0f/5.0f*m2 - 4.0f/5.0f); + float tmp1 = ((14.0f/5.0f) * m2 - (2.0f/5.0f)) * (5.0f/12.0f); cp = Math::pow(tmp0, 3.5) * tmp1; } @@ -91,7 +107,7 @@ float Atmosphere::calcVCAS(float spd, float pressure, float temp) return Math::sqrt((7*p0/rho0)*(tmp-1)); } -float Atmosphere::calcDensity(float pressure, float temp) +float Atmosphere::calcStdDensity(float pressure, float temp) { return pressure / (R * temp); } @@ -101,6 +117,25 @@ float Atmosphere::calcMach(float spd, float temp) return spd / Math::sqrt(GAMMA * R * temp); } +float Atmosphere::spdFromMach(float mach, float temp) +{ + return mach * Math::sqrt(GAMMA * R * temp); +} + +float Atmosphere::spdFromVCAS(float vcas, float pressure, float temp) +{ + // FIXME: does not account for supersonic + float p0 = getStdPressure(0); + float rho0 = getStdDensity(0); + + float tmp = (vcas*vcas)/(7*p0/rho0) + 1; + float cp = ((Math::pow(tmp,(7/2.))-1)/(pressure/p0)) + 1; + + float m2 = (Math::pow(cp,(1/3.5))-1)/0.2; + float vtas= spdFromMach(Math::sqrt(m2), temp); + return vtas; +} + void Atmosphere::calcStaticAir(float p0, float t0, float d0, float v, float* pOut, float* tOut, float* dOut) {