Heterogeneous condensation in the free jet of the coaxial nozzle

Contrails frequently appear in the activities of air vehicles. The Euler-Euler approach based on the quadrature method of moments with the k-ω SST turbulence model is used to simulate the free jet of the coaxial nozzle with heterogeneous condensation to explain the shape, number density, and size distribution of contrails. The investigation analyzes the formation mechanism of the contrail and the flow characteristics of the free jet and obtains the parameters of the contrail. The results reveal that considering the turbulence effect on the particle phase, the diffusion of the particles and the gaseous species has a similar performance in the main section of the jet. With heterogeneous condensation, which consumes a component of the vapor, the particle sizes sharply increase, causing the vapor mass fraction of the jet to considerably decrease and the particle number density and volume fraction distributions to become dislocated. The absolute content of vapor is too small; therefore, the condensation heat release only increases the jet temperature by 0.5 K, whose effect on the jet development can be ignored. The formed ice crystals almost do not disappear inside the computational domain because the increase rate of the particle sizes is far greater than the reduction rate in the computational domain. The particle size distribution develops from dispersion to concentration, finally presenting an approximately normal distribution, whose particle sizes are mainly concentrated in 0.8-2.0 μm, accounting for approximately 83% of the particle total in the contrail, as the contrail shape develops in the computational domain from a ring shape to a pear shape, finally presenting a cone shape.