Direct simulation Monte Carlo (DSMC) method with simplified Bernoulli-trials(SBT) collision scheme has been used to study the rarefied pressure-drivennitrogen flow through diverging microchannels. The fluid behaviours flowingbetween two plates with different divergence angles ranging between 0$^{circ}$to 17$^{circ}$ are described at different pressure ratios(1.5${le}{prod}{le}$2.5) and Knudsen numbers (0.03${le}$Kn${le}$12.7). Theprimary flow field properties, including pressure, velocity, and temperature,are presented for divergent microchannels and are compared with those of amicrochannel with a uniform cross-section. The variations of the flow fieldproperties in divergent microchannels, which are influenced by the area change,the channel pressure ratio and the rarefication are discussed. The results showno flow separation in divergent microchannels for all the range of simulationparameters studied in the present work. It has been found that a divergentchannel can carry higher amounts of mass in comparison with an equivalentstraight channel geometry. A correlation between the mass flow rate throughmicrochannels, the divergence angle, the pressure ratio, and the Knudsen numberhas been suggested. The present numerical findings prove the occurrence ofKnudsen minimum phenomenon in micro- and Nano- channels with non-uniformcross-sections.
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