应用激光流体应变率仪测量壁面阻力

激光流体应变率仪是能将流体边界层的近壁区线性速度分布与菲涅尔双棱镜分光形成的干涉条纹的间距线性特性结合起来的测量仪器,能够直接测量固体表面边界层的速度梯度,而且不干扰流场,并由速度梯度可推出壁面剪切应力。用这种仪器在二维流动管道中进行了测量层流和湍流的初步试验。试验表明,对层流的测量结果与理论分析基本一致。因此,该仪器可作为流体边界层的壁面阻力测量及监视工具。

MEASUREMENT OF WALL FRICTION BY USING LASER FLUID STRAIN RATE METER

This paper describes a laser fluid strain rate meter, which can be used to measure directly the velocity gradient in the boundary layer on the surface of an object without disturbing the flow field. The wall shear stress can be derived from the velocity gradient. The principle and experimental technique of local shear stress measurement are discussed in detail. The linear velocity variation in the viscous sub-layer could be combined with a modified laser anemometer system for the purpose of shear stress measurement. Preliminary experiments in a two-dimensional channel were carried out for both laminar and turbulent flow. The results for laminar flow showed a good agreement with theoretical analysis. The method provides a tool for measuring and monitering wall friction in the boundary layer in a non-intrusive manner.