Numerical simulation was conducted with CFD software ANSYS CFX to investigate the characteristics of gas flow in a rectangular microchannel with a hydraulic diameter of 0.4mm. Three flow models

namely

γ-Reθt model

laminar model and shear stress transport (SST) model

were taken in the simulation. The simulation results were compared with the experimental data. Results indicate that laminar model and SST model are incapable of predicting transition. γ-Reθt model forecasts the critical Reynolds number well and the relative errors of friction factor keep under 20%. Before Reynolds number reaches the critical value

local turbulent regions appear at the rear of the microchannel and the regions expand with the growing Reynolds number. The streamwise position where the inlet and the rear turbulent regions meet is almost identical with the position where the skin friction reaches its minimum value.