speed of sound as function of density and temperature
function velocityOfSound_dT extends Modelica.Icons.Function; input SI.Density d "density"; input SI.Temperature T "temperature"; input Integer phase = 0 "2 for two-phase, 1 for one-phase, 0 if not known"; input Integer region = 0 "if 0, region is unknown, otherwise known and this input"; output SI.Velocity v_sound "speed of sound"; end velocityOfSound_dT;