摘要
本文現場試驗的方式探討天然河道測線表面流速與平均流速的關係。有鑑於國內並無非接觸式流速觀測儀檢測研究，本研究針對非接觸式流速觀測儀進行檢測，相關結果不僅能幫助瞭解儀器之特性，所發展之檢測流程亦可提供後續研究參考；針對天然河道測線表面流速與平均流速關係的探討，測線平均流速觀測利用普萊氏流速儀進行，表面流速觀測包括SVR雷達測速槍進行非接觸式表面流速量測及普萊氏流速儀表面0.1倍水深流速量測兩種方式，研究結果提供流量觀測人員以表面流速迅速推求平均流速之解決方案，縮短人員於惡劣天候環境之作業時間，進而降低其作業風險。
試驗結果顯示，本研究所採用之非接觸式表面流速量測儀器SVR容易因為顯示精度之關係，於觀測流速較小時產生與真實流速之差異，然此項差異將隨著真實流速提高逐漸降低，由於 SVR表面流速儀多應用於洪水流速觀測，於實務應用觀測表面流速此項差異可以忽略；以SVR雷達測速槍觀測之表面流速與平均流速之實測轉換係數約介於0.5~0.6之間，遠低於理論轉換係數0.86，高流速時觀測點愈偏離推估之轉換關係式，利用SVR雷達測速槍觀測之表面流速推估平均流速時宜審慎評估。以普萊氏流速儀量測0.1倍水深流速為代表表面流速，各流量測站表面流速與平均流速之實測轉換係數約介於0.82~0.99之間，與理論轉換係數0.86相去不遠，各測站之轉換關係穩定，然部分站於特定流速之情況下，表面0.1倍水深流速與平均流速關係，出現與整體資料趨勢不同之情況，未來之研究建議針對此現象再深入探討。
關鍵詞：表面流速、平均流速、雷達測速槍、普萊式流速儀

ABSTRACT
Detailed measurements of flow velocities were presented. Emphasis is given to the relation between the surface velocity and averaged velocity. The experiments comprised measurements of flow velocities for three types, including surface velocity by a noncontact measurement (SVR), surface velocity by a contact measurement (Price current meter) and averaged velocity by a contact measurement (Price current meter). In additions, apply correction tests for SVR was conducted in two laboratory flumes. The measurement equipment error analysis and test procedures have been carried out.
The SVR test had uncertainty error in the conditions of low flow velocities due to the low display precision of SVR. It is shown that a significant reduction of the uncertainty error by increasing the flow velocity. Generally, the SVR are used in measurement of surface velocity during high flow condition. Therefore, the uncertainty error could be ignored in the practical engineering. The conversion coefficients for surface velocities measured by SVR and averaged velocities are ranging from 0.5 to 0.6, which are much lower than the theoretical value of 0.86. As a result, the measured data are deviated the rating relation during the high flow condition. Using a SVR as velocity measuring equipment needs to be careful while the surface velocities are high. The conversion coefficients for surface velocities measured by Price current meter and averaged velocities are ranging from 0.82 to 0.99, which are close to the theoretical value of 0.86. However, the rating relations are deviated in low and high flow conditions. The data of high velocities need more attentions in the future researches.
Keywords: Surface Velocity, Averaged Velocity, SVR, Price Current Meter.

參考文獻
1. ISO 748(1979 E), Liquid flow measurement in open channels-velocity area methods.
2. Plant, W. J. and W. C. Keller, (1990a), Cross sections and modulation transfer functions at L and Ku bands measured during the tower ocean wave and radar dependence experiment, Journal of Geophysical. Research, Vol. 95, No. C9, pp. 16,277-16,289.
3. Plant, W. J. and W. C. Keller, (1990b), Evidence of Bragg scattering in microwave Doppler spectra of sea return, Journal of Geophysical. Research, Vol. 95, No. C9, pp. 16,299-16,310.
4. Rantz, S. E., and others, (1982a), Measurement and computation of streamflow, Vol. 1. Measurement of stage and discharge, U. S. Geological Survey Water Supply Paper 2175, U.S. Geological Survey.
5. Rantz, S.E., and others, (1982b), Measurement and computation of streamflow, Vol. 2. Computation of discharge, U. S. Geological Survey Water Supply Paper 2175, U.S. Geological Survey.
6. Water Measurement Manual (2001), United States Department of the Interior Bureau of Reclamation.
7. Whalleyl, N., R. S. Iredale and A. F. Clarel, (2001), Reliability and uncertainty in flow measurement techniques - some current thinking, Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science, Vol. 26, No. 10-12, pp. 743-749.
8. Yorke, T. H. and K. A. Oberg, (2002), Measurement river velocity and discharge with acoustic Dopple profilers, Flow Measurement and Instrument, Vol. 13, pp. 191-195.
9. 台灣省水利局(1982)，水文觀測實務。
10. 四國地方整備局河川部、四國水文観測檢討會(2004)，水文観察の手引き(案) –低水流量観測編(第2版)，日本。
11. 四國地方整備局河川部、四國水文観測檢討會(2004)，水文観察の手引き(案) –高水流量観測編(第2版)，日本。
12. 經濟部水利署「因應氣候變遷河川流量觀測技術研發及建置先期計畫」(2010)
13. 經濟部水利署「河川流量量測技術革新研究計畫」(2005)
14. 李明靜(2003)，河川表面流速與流量非接觸式量測方法之發展及應用，國立成功大學水利及海洋研究所博士論文。