Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/13555
標題: 投潭水流作用下沖刷坑特性與渠床剪應力變動之研究
Shear Stress Distribution on Channel Bed of a Scour Hole by Free Overfall
作者: 賴泰榮
Lai, Tai-Zon
關鍵字: Scour Hole;沖刷坑;Scour Hole Characteristics factor;Shear Stress;Variation of Free Overfall Shear Stress;沖刷坑特徵因子;剪應力;投潭剪應力變動
出版社: 土木工程學系
摘要: 
本研究之主要目的係利用標準砂為渠床質所得局部沖刷試驗之結果設計
一系列模擬投潭水作用下之動床沖刷坑型態以裝設於渠床底之剪應力裝置
經由電腦抓取其所輸出之訊號進行數位類比處理量測沖刷坑底部之剪應力
分佈配合精密之電磁流速計檢測堰壩下游的流速場來探討沖刷坑變化與剪
應力分佈間之關係以及局部沖刷過程中剪應力所扮演之角色期為日後有關
投潭水流局部沖刷相關研究提供進一步之認知.

AbstractThe main objective of this study was to investigate the
variations of the distribution of shear stress along the scour
hole downstream of a weir during the evolution of the scour
hole.The shapes of the scour hole were selected based on the
results of the local scour testswith standard sand. An
electromagnetic current was used to measure the flow field in
theplunge pool. Based on the analysis of the laboratory dada, it
was found that in general the scour holecan be described with
two straight lines and one curve or semi-circle. An
exponentialfunction was used to describe the dimensionless
maximum scour depth. Expressionsfor the unit erosion rate and
area factor were also developed. These function and
expressionwere proved by other investigators.Both the energy and
momentum correction factors, trere were found to increase from
the toe of the weir. Their values remained in the same order of
magnitude along the first straight lineof the scour hole. The
values of both increased for one to three order of magnitude
alongthe curved portion of the hole due to the free overfall jet
impact. The values decreased tobe around 1 along the second
straight line due to the dissipation of energy. The
relationshipof alpha and bata was also satisfied along the
second straight line of the scour hole.The shear stress was
found to decrease in the downstream direction of the scour hole
forboth the results of strain transducter and strain gages.
These results were probably dueto the fact that the energy
dissipated in the downstream direction. For a given distragethe
value of the shear stress decreased with time, and eventually
approached the criticalshear stress of the sand particle.
URI: http://hdl.handle.net/11455/13555
Appears in Collections:土木工程學系所

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