In this study we use direct simulation Monte Carlo (DSMC) method to simulate subsonic nitrogen flow through micro/nanoscale backward-facing step. This paper investigates the effect of Knudsen number on the fluid and thermal behavior of the step geometry. We observed that increasing the Knudsen number makes remarkable variations in flow behavior such as decreasing in average flow Mach number and increasing in average flow temperature. Our results showed that variations in flow and thermal field properties are more sensible at low Knudsen number. Also the results show that increasing Knudsen number decrease the length of separation zone behind the step. Additionally, gas flow becomes more uniform at higher flow Knudsen number.

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