  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 microchannels. The fluid behaviours flowing
between 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). The
primary flow field properties, including pressure, velocity, and temperature,
are presented for divergent microchannels and are compared with those of a
microchannel with a uniform cross-section. The variations of the flow field
properties in divergent microchannels, which are influenced by the area change,
the channel pressure ratio and the rarefication are discussed. The results show
no flow separation in divergent microchannels 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
microchannels, 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 Nano- channels with non-uniform
cross-sections.
