On different kinetic approaches for computing planar gas expansion under pulsed evaporation into vacuum

Abstract

The numerical study of one-dimensional gas expansion under pulsed evaporation into vacuum is carried out on the basis of the direct simulation Monte Carlo method, the exact Boltzmann kinetic equation, and the S-model kinetic equation. The results are presented for various levels of evaporation intensity, defined by the amount of evaporated material. Special attention has been paid to the calculation of the average axial energy of particles, the velocity vector of which deviates from the axis by no more than a small prescribed angle α. This characteristic of the flow is important for analysis of time-of-flight distributions in pulsed laser ablation. It is found that for intense evaporation, the average axial energy has a maximum as a function of time. The presented results allow us to establish the relative accuracy of the considered kinetic approaches for various flow regimes.