DSMC investigation of rarefied gas flow through diverging micro- and nanochannels

摘要

Direct simulation Monte Carlo (DSMC) method with simplified Bernoulli trials (SBT) collision scheme has been used to study the rarefied pressure-driven nitrogen flow through diverging micro-and nanochannels. The fluid behaviours flowing between two plates with different divergence angles ranging between 0 degrees and 17 degrees are described at different pressure ratios (1.5 <= Pi <= 2.5) and Knudsen numbers (0.03 <= Kn <= 12.7). The primary flow field properties, including pressure, velocity, and temperature, are presented for divergent micro-and nanochannels and are compared with those of a micro-and nanochannel with a uniform cross section. The variations of the flow field properties in divergent micro-and nanochannels which are influenced by the area change, the channel pressure ratio, and the rarefication are discussed. The results show no flow separation in divergent micro-and nanochannels for all the range of simulation parameters studied in the present work. It has been found that a divergent channel can carry higher amounts of mass in comparison with an equivalent straight channel geometry. A correlation between the mass flow rate through micro-and nanochannels, the divergence angle, the pressure ratio, and the Knudsen number has been suggested. The present numerical findings prove the occurrence of Knudsen minimum phenomenon in micro-and nanochannels with non-uniform cross sections.