Kinetic Model of Condensation in a Free Argon Expanding Jet

The direct-simulation Monte Carlo (DSMC) method has recently been developed to simulate homogeneous condensation in a free-expansion rocket plume. However, cluster‐monomer and cluster‐cluster collision models as well as the determination of cluster size were simplified in the previous work, and the effect on the accuracy of the numerical simulation results was not quantified. In this work, the molecular-dynamics (MD) method is used to simulate collision and sticking probabilities for argon clusters and the results are compared with the hard-sphere model. These improved models are then integrated into a DSMC code to predict the Rayleigh scattering intensity in a free-expanding argon condensation plume, and numerical results are compared with experimental data along the plume centerline. Nomenclature A = constant B = constant b = impact parameter c =v elocity d = diameter E = evaporation rate or energy I = intensity i = number of atoms J = nucleation rate K = intensity constant k B = Boltzmann’s constant L = specific latent heat M = cluster mass m = molecular mass N = number density nc = number of simulated nuclei particles ps = saturation pressure q = sticking coefficient R = ideal gas constant r = distance or radius T = temperature V = interaction potential or specific volume α = species polarizability � t = time step � V = cell volume � = potential constant λ0 =w avelength ρ = density σ = surface tension or potential constant Subscripts