Numerical investigation of the effect of micro channel bends angle

A pressure driven compressible gas flow through three-dimensional microchannel with bend of various angles is investigated using Navier Stokes equations coupled with the first-order Maxwell slip boundary condition along with Smoluchowski temperature jump definition. A wide range of bend angles from 60 to 180 is considered. The details of the flow structures near the corner are analyzed, investigating the competing effects of rarefaction, compressibility and geometry on the channel performances. The bent results are compared to those from the equivalent straight micro-channel geometry in terms of mass flow rate and Poiseuille number. The analysis of the flow structure shows that the channel geometry is important in microfluidic applications. In particular, it is found that a micro-channel with bend angle less than 90 degrees produces an increase in mass flow with respect to the straight one, while obtuse angle bends produce a mass flux reduction. For the sharp angle the flow separation and recirculation occur in the corner of the bend and this becomes more critical as the bend angle decreases. The rarefaction alleviates the geometry effect, while compressibility enhances it.