声学多普勒流速仪在水槽流速测量中的应用

Application of Acoustic Doppler Velocimetry in Flume Flow Experiment

针对声学多普勒流速仪(ADV)运用于清澈水质的水流中精度较低的问题,采用了一种向清澈水流中掺混适量悬浮颗粒物的方法显著提高ADV的测量精度。通过对比掺混悬浮颗粒物与清澈水质中ADV的流速测量结果,发现掺混适量悬浮颗粒物后,流速测量数据明显更稳定,符合水槽流场的实际情况。给出了悬浮颗粒物的推荐含量为106 g/m^3。采用该方法,在水槽中沿垂向布置10个流速测点,通过调整水泵变频器频率来改变流速,测量了不同流速时的水槽断面垂向流速分布。发现流速沿垂向分布不均匀,呈线性剪切流分布。水槽出流口的布置方式和水槽壁面及底面摩阻是产生断面流速沿垂向分布不均匀性的原因。最后,通过最小二乘法拟合给出了水泵变频器的频率与断面平均流速的线性关系。

Aiming at the problem of the low accuracy of Acoustic Doppler Velocimetry（ADV） used in clear water flow,a method of mixing suspended particles into the clear water is presented to improve the accuracy of ADV. By comparing the measurement results of ADV in the water flow with mixed suspended particles and the clear water,it is observed that the flow velocity of the former situation is obviously more stable,the result meets with the actual stable uniform flow of the water flume. The suggested content of the suspended particles in this test is 106 g/m～3. Ten velocity measuring points are arranged vertically in the water flume. The flow velocity is changed by adjusting the frequency of the converter of a pump. This method is used to measure the vertical distribution of the flow velocity of the water flume. It is observed that the flow velocity is not uniformed along the vertical direction,and is followed the linear shear flow distribution. The reasons for this uneven distribution are the arrangement of outflow port and the friction of the lateral and bottom walls of the water flume. Finally,the linearly relationship between the frequency of converter and mean vertical velocity is presented by the means of least square method.