壁面摩擦应力直接测量技术探讨

自行研制了一台采用误差抵消校准法的阻力天平仪，在一定的雷诺数范围内，对风洞内壁光滑平板壁面，用此天平仪测量了流体的摩擦应力及摩擦系数，用ＩＦＡ３００型热线风速仪测量了相应雷诺数下边界层的平均速度分布，然后 似律法和布拉修斯经验公式分别计算了摩擦应力及磨擦系数。结果对比表明，采用的原理及校准方法合理，所制作的天平仪在试验雷诺数范围内，具有较高的测量精度衅小的相对误差，适用于边界层特性的研究和开发。

Measurement of Flow Friction Stress in Plane Boundary Layer

A computer controlled balance is made to measure the flow skin friction. Since the calibration error arises mainly from the bearing friction force, the error removal calibration method is deve loped instead. Positive error from the bearing is first introduced by increasing the load slowly, it is then decreased slowly so that negative error is introduced. By averaging positive and negative errors such that the bearing error could be removed. For three Reynolds numbers the balance is used to measure skin friction on the plane boundary layer. An IFA300 thermal anemometry is used to measure the average velocity distribution in the boundary layer. The friction coefficient is then computed by using the method of the average velocity distribution similarity law and Blassius formula. The difference is analyzed; it shows that the adopted calibration method is reasonable and the balance is good enough to be used in the study of the plane boundary layer.