Numerical simulation of flow transition in microchannel

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. 4 mm. Three flow models, namely, γ-Re_θt 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-Re_θt 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.