中文摘要：

利用实验方法研究了粗糙度对矩形截面微管道内液体流动阻力特性的影响，采用微观粒子图像测速技术测量了粗糙微管道内的流场结构。实验结果表明：在层流状态下，3％-7％的相对粗糙度可以导致微管道内流动阻力的明显增加，在粗糙单元附近形成的压差阻力是导致流动阻力增加的主要原因，粗糙单元还会引起微管道内的流动失稳，导致粗糙微管道内层流向湍流的转捩提前。

英文摘要：

The effect of surface roughness on the frictional characteristics of the liquid flow in the microchannels with distributed rectangular roughness elements is experimentally studied. The velocity fields are obtained by micro particle image velocimetry （micro-PIV）. The friction coefficients in the microchannels with 3%-7% relative roughness are higher than the prediction based on the conventional theory due to the additional pressure drag caused by roughness elements. The existence of roughness elements gives rise to additional disturbance in the laminar stream, and the early transition to turbulent flow in the rough microchannels is validated.