Slip Flow Structures in Confined Geometries

This paper presents various flow structures related to velocity slip and temperature jump in very low Reynolds number gas flow. The structures differ significantly from the ones observed in continuum regime for laminar flow, especially if the geometry has complex structure, which is very often the case in microfluidic devices. We are modelling the flow as a continuum Navier-Stokes gas flow with additional velocity slip and temperature jump boundary conditions for curved surfaces for slip flows with Knudsen numbers Kn < 0.1. For complex channel geometries with obstacles and curved walls vortex patterns are observed that are related to the thermal stress slip flow. This type of flow is induced only when non-uniform temperature distributions inside flow domains are present. The investigated geometries consist of one or more cylinder walls with diameters of up to a few 100 μm placed inside of confined microchannels, with all setups being two-dimensional. In gaseous microdevices the resulting complex flow patterns can be utilised to enhance mixing or heat transfer.