  The gas flow characteristics in lid-driven cavities are influenced by several
factors, such as cavity geometry, gas properties, and boundary conditions. In
this study, the physics of heat and gas flow in cylindrical lid-driven cavities
with various cross-sections, including fully or partially rounded edges, is
investigated through numerical simulations using the direct simulation Monte
Carlo (DSMC) and the discrete unified gas kinetic scheme (DUGKS) methods. The
thermal and fluid flow fields are systematically studied for both constant and
oscillatory lid velocities, for various degrees of gas rarefaction ranging from
the slip to the free-molecular regimes. The impact of expansion cooling and
viscous dissipation on the thermal and flow fields, as well as the occurrence
of counter-gradient heat transfer (also known as anti-Fourier heat transfer)
under non-equilibrium conditions, are explained based on the results obtained
from numerical simulations. Furthermore, the influence of the incomplete
tangential accommodation coefficient on the thermal and fluid flow fields is
discussed. A comparison is made between the thermal and fluid flow fields
predicted in cylindrical cavities and those in square-shaped cavities. The
present work contributes to the advancement of micro/nano-electromechanical
systems (MEMS/NEMS) by providing valuable insights into rarefied gas flow and
heat transfer in lid-driven cavities.
