Simulation of gas flow in microchannels with a single 90°90° bend

Bends are frequently encountered in microdevices and therefore a fundamental understanding of flow through them is important. In this paper, we have used the lattice Boltzmann method to study flow of a gas through a microchannel with a single 90°90° bend. The computations are two-dimensional, isothermal, and for the Reynolds and Knudsen numbers typically observed. We find that the pressure drop in segments of equal lengths before and after the bend is different, and a recirculatory motion is seen near the bend even when the flow Reynolds number is less than unity. The velocity and pressure distribution between the bend and straight microchannels is almost identical at large Knudsen numbers, indicating that the flow does not feel the presence of the bend in such cases. This is attributed to rarefaction of the gas which hinders transfer of information across the flow.