指數形渠道之投潭水躍特性研究

Hydraulic Jump in Exponential Channel by Free Overfall Flow

陳正炎(JEN-YAN CHEN)

《台灣水利》 38卷4期 (1990/12) Pp. 50-59+49

https://doi.org/10.6937/TWC.199012_38(4).0003

摘要

本文係藉以推理、分析與比較，加之特例驗證，旨在探討指數形水平渠道受投潭作用產生水躍現象，其水躍的特性行為與消能功效，期能提供更多不同形狀渠道對投潭消能之認知。研究結果得共軛水深比Ø、相對能量損失△E/E_i及投潭消能效率η，不但與躍前福祿數F_i、相對堰高H有關，而且亦將受特徵冪次n影響，顯示n（1.0≦n≦2.0）值大者為水躍特性佳、消能功效大。另外，當H＞4時，拋物形（n=1.5）渠道之η值與三角形（n=2.0）者相近。文中並發展拋物形渠道之η=η（H）近似公式，以作為堰壩下游消能效率之估算或預測用。

並列摘要

In this study, a horizonal exponential channel is used to investigate the characteristic behavior of jumps under the free overfall flow in weir. The results were analyzed and compared through three special cases in order to obtain more knowledge of the influences of energy dissipation by channel shapes. It was observed from the results that the conjugate depth ratio Ø, relative energy loss △E/E_i and energy dissipation efficiency η were not only influenced by the Froude number F_i and dimensionless height of weir H, but also by the characteristic power n. The findings indicate that large value n (1.0≦n≦2.0) of channels can produce a higher relative energy dissipation. On the other hand, good agreements of η have been obtained between the parabolic (n=1.5) and triangular (n=2.0) channels when H>4. Finally, an approximate formula η=η(H) of the parabolic channel has been developed for calculation as well as prediction of the energy dissipation efficiency of the downstream in weir.