坡面水流滚波特征参数超声波自动测量系统构建与试验

Establishment and experiment of ultrasonic measuring system for characteristic parameters of roll waves on slope surface

精确高效的观测手段是深入研究坡面薄层水流特性的基础。基于系统集成理论和自动化测量原理,结合高精度超声波水位传感器,研制坡面水流滚波特征参数测量系统。在光面玻璃床面,5种坡度和5种单宽流量条件下进行实际测量应用,评价测量系统的精确度及稳定性,并与人工测针法和目测法测量结果比较分析。结果表明,测量数据相对误差为0.23%,变异系数为0.66%;测量系统和传统测量方法测得的滚波波峰值最为接近,滚波频率、波速和波长的接近程度依次减弱;相比人工测量方法,超声波测量操作简便,自动化程度高且能够进行持续稳定观测,具有较好地测量精度和可靠性,能够满足坡面水流滚波特性研究需求。研究成果在坡面水流测量手段改进方面具有广阔的运用前景。

The precise study of free surface flows is explored mostly because of their importance in construction of soil erosionmodels. The accurate and efficient observation methods can lay a solid foundation for the further study of characteristics ofslope flow. The objective of this work was to design an experimental system for measuring roll waves. The system was basedon a high-precision ultrasonic sensor. The measurement system was composed of ultrasonic sensors, data acquisition box andthe computer. The experiment was carried out in a hydraulic flume. The unit discharge varied from 0.167 to 0.500 L/（m. s）, andslope gradient was from 3°to 15°. The system was calibrated and the results showed that the average relative error of themeasurement system was 0.23%. The average coefficient of variation was 0.66%. The main parameters of roll waves includedwave velocity, wave frequency, wave length and wave peak. In this study, by recording roll waves observed in the samesection, the relationship between water depth and time was obtained by ultrasonic flowmeter. The average interval time of dataacquisition was 15 ms so that the sensor could catch the change of water level in time. Roll wave frequency was obtained byobserving the cross section peaks in unit time. Wave velocity could be obtained by two sensors. The two sensors recorded thetime that the same roll wave passed through the section and also measured the distance of the two sensors. The wave velocitywas calculated as the ratio of distance and duration. The wave length was calculated by the wave velocity and the frequency.The results measured by the proposed system were compared with that obtained from the stylus method and visual method.The results showed that the wave peak measured by the system was mostly similar with that from the stylus method, followedby roll wave frequency, wave velocity and wave lengths. The measuring system had better accuracy and reliability to reachmeasurement requirements of characteristic parameters of roll waves on slope surface. For the same observation section, therolling wave was not constant in the measurement process. The wave peak, wave velocity and the frequency had the averagecoefficient of variation of 0.238, 0.806 and 0.430. The ultrasonic measuring system can continuously work and provide reliablemeasurements for roll wave parameters. As compared with the conventional method, the measuring system greatly reduced testtime and effort to improve test efficiency. The research results have wide application foreground in the improvement of thewater flow measurement method on the slope surface.