der(Density) computation for Dry Air Ideal Gas (inputs: P, T, der(P), der(T))
function derDensity_derP_derT input Units.SI.Pressure P; input Units.SI.Temperature T "Temperature (K)"; input Real der_P "pressure time derivative (Pa/s)"; input Real der_T "Temperature time derivative (K/s)"; output Real der_rho "density time derivative (kg/(m3*s))"; end derDensity_derP_derT;