Kinetic analysis of hypersonic laminar separated flows for hollow cylinder flare configurations

The direct simulation Monte Carlo method was used to study hypersonic laminar flow around hollow cylinder flare configurations. Three configurations with different flare shape and length were considered. This made it possible to estimate the effect of expansion at the trailing end of the flare on the separation region and shock/shock interaction. The results obtained showed that the separation region extent is identical for all configurations for the freestream conditions considered. Nevertheless, the shock/shock interaction region is very close to the end of the flare with the smallest length, which requires particular attention to the computational grid and even to the numerical code. Even small differences in numerical codes may possibly lead to a qualitative change in the flowfield structure. Therefore, for further numerical and experimental studies of this problem, it is necessary to use the configuration with an extended flare because, in this case, the influence of expansion is definitely suppressed. Particular attention was paid to reliability of numerical results and the influence of the grid cell size on calculated flow properties. A cell Knudsen number was used to estimate the quality of the computational grid and to generate a sufficient well-resolved grid.