A DSMC investigation of gas flows in micro-channels with bends

Pressure-driven, implicit boundary conditions are implemented in an open source direct simulation Monte Carlo (DSMC) solver, and benchmarked against simple micro-channel flow cases found in the literature. DSMC simulations are then carried out of gas flows for varying degrees of rarefaction along micro-channels with both one and two 90-degree bends. The results are compared to those from the equivalent straight micro-channel geometry. Away from the immediate bend regions, the pressure and Mach number profiles do not differ greatly from those in straight channels, indicating that there are no significant losses introduced when a bend is added to a micro-channel geometry. It is found that the inclusion of a bend in a micro-channel can increase the amount of mass that a channel can carry, and that adding a second bend produces a greater mass flux enhancement. This increase happens within a small range of Knudsen number (0.02 ⩽ Knin ⩽ 0.08). Velocity slip and shear stress profiles at the channel walls are presented for the Knudsen showing the largest mass flux enhancement.

► Separation regions can exist at sharp corners in low Re micro-scale flows.
► Adding a bend to a micro-channel can increase the mass-carrying capacity.
► Two bends increases the mass flux enhancement further.
► Enhancement is restricted to a small range of Knudsen number.
► Pressure plots show different behaviour in the mass flux enhancement range.