水工構造物易受水流沖擊造成損壞，故如何保護其不受水流破壞，實為一水利工程設計者應考量之重要問題。本研究乃依據明渠水能量削減原理，探討漸擴形渠道之水躍消能現象，並分別與矩形、三角形及拋物形等斷面渠道比較之。研究結果獲得漸擴形渠道水躍現象之相對能量損失及投潭消能效率，不但與躍前福祿數 、相對堰壩高 有關，且亦將受水躍前後渠道斷面寬度比影響。綜觀比較分析獲致流況相同時，投潭消能效率以漸擴形渠道( )為佳，其次依序分別為三角形渠道、拋物形渠道、矩形渠道，且值愈大投潭消能效率值愈高。

Water flowing with high velocity is capable of causing erosion damage to hydraulic structures. How many protection works should be designed to reduce the harmful damage is an important issue for hydraulic designers. This study aims to analyze the energy variation of hydraulic jump under the
free overfall flow in a gradually expanding channel. It was observed from the results that, the relative energy loss and the energy dissipation efficiency were not only influenced by the Froude number and the dimensionless height of weir , but also by the channel width ratio. Comparing with the index channels which were rectangle, triangle, and parabolic shows that according the superiority of energy dissipation efficiency , it falls into the ranks as gradually expanded channels ( ), triangular channels, parabolic channels, rectangular channels. In other words, the greater the channel width ratio , the higher efficiency of energy dissipation were found.