Flow characteristics in a trapezoidal silicon microchannel

In this paper, global pressure drop and velocity field were experimentally investigated for water flow in a trapezoidal silicon microchannel with a hydraulic diameter of 237 µm. Microscopic particle image velocimetry (micro-PIV) is used to obtain the velocity profiles at different locations of the microchannel for Reynolds numbers between 50 and 2800. For Re > 700, Δp–Re relationship deviates from the linear behavior and the deviation depends on the Re. The experimental results of the velocity field show that the deviation is due to the entrance effect in microchannel, and the entrance length in our experiments can be predicted byLe/Dh = (0.08–0.09)Re. Velocity profiles and root mean square values of the fluctuating velocity along the centerline obtained by micro-PIV indicate that the transition from laminar flow to turbulent flow occurs for Reynolds number ranging between 1500 and 1800. This result is consistent with the global measurements of the pressure drop.