Semiempirical Model for Homogeneous Nitrogen Condensation in Hypersonic Wind Tunnels

A semiempirical density gradient theory (DGT) is used to model nanoscale nitrogen droplets formed by homogeneous nucleation. The constant of the inhomogeneous DGT term is found using planar surface tension values and recent nucleation rate measurements from available literature. Resulting values for the free energy barrier, surface tension, and mean density of critical droplets are used in nucleation and droplet growth rate models to evaluate the condensation process. Good agreement is found between this model and published values for condensation onset in hypersonic wind tunnels, with an average deviation of 2.2 K in static temperature.