應用攝影測量技術量測灌溉渠道表面流速與推估流量之研究

Application of Photogrammetric Techniques to Measure Surface Velocity and to Estimate Discharge in the Irrigation Channel

柳文成(Wen-Cheng Liu) ； 黃偉哲(Wei-Che Huang) ； 毛培宇(Pei-Yu Mao)

《農業工程學報》 62卷2期 (2016/06) Pp. 40-53

https://doi.org/10.29974/JTAE.201606_62(2).0004

摘要

台灣現行之渠道/河川於常流量時期量測流速時大多使用侵入式測量，量測人員進入水體中除了增加了量測任務之風險外，也增加了水體之擾動。於洪流量時期因人員無法進入水體中，渠道/河川皆使用浮標法來進行流速之量測，但因浮標法之操作方式會造成不確定之人為誤差。因此本研究使用非接觸性之攝影測量，進行渠道表面流速量測，進而推估流量。本研究藉由顆粒影像速度法(Particle Image Velocimetry, PIV)及顆粒追蹤速度法(Particle Tracking Velocimetry, PTV)量測苗栗市境內一農業用灌溉渠道之表面流速，並搭配數值水流流速儀量測之斷面平均流速，建立指標流速法；並比較PIV 及PTV 兩種量測方法何者較適用於該渠道，結果顯示PIV 法較適用於渠道之表面流速量測。影像量測之表面流速可透過指標流速法換算成斷面平均流速後，以獲得流量資料。另外，本研究亦使用雙相機來擷取渠道影像，希望透過提高影像之解析度，以增加影像量測之準確度，經與單相機量測結果比較，其均方根誤差相對百分比較單相機量測結果低，顯示使用雙相機所量測之表面流速較單相機量測結果為佳。

關鍵字

灌溉渠道 ； 顆粒影像速度法 ； 顆粒追蹤速度法 ； 指標流速法 ； 雙相機

並列摘要

In Taiwan, an invasive method is popularly used to measure velocity in rivers/ channels during normal flow periods. Researchers/staffs come into the water not only to increase the potential risk, but also to disturb water body. During the high flow periods, velocity in rivers/channels only can be measured using the buoy method which easily results in errors and uncertainties due to the manual operations. Therefore, the utilization of noncontact photogrammetric technique is highly expected to measure surface velocity for estimating discharge. In the present study, the Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) were adopted to measure surface velocity in the irrigation channel of the Miaoli City. The flow current meter was also used to measure cross-sectional averaged velocity for building index-velocity. To find out which method is suitable for measure surface velocity in the irrigation channel, the measured results with PIV and PTV methods are compared. It showed that PIV method is suitable to measure surface velocity comparing to PTV method. Measured surface velocity with PIV method can be used to calculate the cross-sectional averaged velocity based on the index-velocity and then to obtain discharge. In addition, dual-camera system was used to catch images in the channel to increase image resolution and to enhance the accuracy of surface velocity. Comparing the measured results with single camera and dual-camera, the statistical values of relative root mean squared error using dual-camera system is lower than using single camera. The results indicated dual-camera system would be better for measuring surface velocity.

並列關鍵字

Irrigation channel ； Particle Image Velocimetry (PIV) ； Particle Tracking Velocimetry (PTV) ； Index-velocity method ； Dual-camera