Investigation of Wall Effects on Flow Characteristics of a High Knudsen Number Nozzle

Two-dimensional direct simulation Monte Carlo (DSMC) was used to investigate the effect of wall accommodation on different modes of operation of a nozzle under high Knudsen number conditions. Substantial performance enhancement was seen at higher values of converging–diverging angles, because a reduction in the surface area-to-volume ratio decreased the wall effects. Though the normal energy accommodation had a negligible influence on the nozzle performance, it was seen to be a critical factor for accurate prediction of gas temperature along the wall. At higher Knudsen numbers, the flow tended to become one-dimensional even for the case of complete accommodation.