一、引言在水力实验室内,测量低流速的要求是普遍的问题。在原型结构容易量测的各种流速,按比例缩小的物理模型中,能低于大多数常规流速仪所测的范围。研究边界层和尾流必然涉及到低流速。同样,由于微小的压力梯度所驱动的流动,诸如由于自然的对流、热层所形成的浮力差以及诱导等引起的流动,往往流速是很慢的,常规方法无法测量。 I. INTRODUCTION In hydraulic laboratories, the need to measure low flow rates is a common problem. The flow rates, scaled-down physical models, which are easy to measure prototype structures, can fall below the range of most conventional meters. The study of the boundary layer and wakes necessarily involves low velocities. Similarly, the flow rate is slow due to the flow induced by a slight pressure gradient, such as due to natural convection, poor buoyancy due to the thermal layer, and induced induction, which conventional methods can not measure.