Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/13735
標題: 降雨對粗糙底床淺水渠流之試驗研究
AN EXPERIMENTAL STUDY ON ROUGH BED CHANNEL EFFECT BY RAINFALL
作者: 劉家盛
Liu, Gan-Shan
關鍵字: Flow visualization;紊流強度;Organized structure;convection speed;雷諾應力;頻譜分析;大小尺度漩渦尺寸
出版社: 土木工程研究所
摘要: 
前人文獻中,關於降雨沖擊淺水流之研究相當有限,且著重於不 降雨強
度對流場的影響,本研究除同時考慮降雨強度及雨滴粒徑之 應外,更針
對不同粗糙底床進行試驗,以延伸試驗領域。研究中採恓砦p射杜普勒
測速儀(Fiber-optic Laser Doppler VelocimetryA簡稱FLDV),來進行速
度流場之量測。循環水槽底部採用均勻玻璃顆刉Q設,分別為0.85mm及8mm
兩種粒徑,進行無降雨及降雨試驗共計103捸A均屬亞臨界流況。本研究之
主要分析項目包括平均速度剖面、二維紊流強度、雷諾應O分佈、Darcy-
Weisbach摩擦係數變化、頻譜分析及大小尺度漩渦尺寸央C此外,並根據
實測資料推導出降雨作用下之主流向及垂向紊流強度嬪G模式,以及流場
底部雷諾應力之平均值與標準偏差之模式,擬供紊坌y場特性分析之參考
。試驗結果顯示,就坡度S<0.3%之試驗而言,當水深粒徑比H/d約<2氶A流
場全深易被雨滴貫穿,當水深粒徑比H/d約>3時,水深不易被雨w貫穿;就
粗糙底床坡度S>0.5%之資料而言,H/d約<1.5以下,流場易Q貫穿;H/
d>2.5時,水深則不易被雨滴貫穿。本研究並針對水深是否Q雨滴貫穿;推
導出兩種紊流強度分佈模式。另一方面,當坡度增大時A降雨對垂向紊流
強度之影響隨之而減小;且坡度為S=0.1%時,主流向峆咻V之無因次化紊
流強度,大致會呈現一常數值,其值分別約為2.0及.0。此外,本研究其
它重要結果如下:1.隨糙度之增大,雷諾數、雨滴仵|及降雨強度對動量
修正係數之影響,會略趨減小。2.隨雨滴粒徑增j及坡度之減緩,雷諾應
力之標準偏差會因而增大。3.摩擦係數f與曼寧Y數 n,因降雨作用而增大
,而當Re>1000以後,則不甚明顯。4.隨糙度S之增大,降雨對頻率能譜圖
影響愈趨不明顯;在近水面處,降雨使不P頻率之能量重新分配。5.大小
尺度漩渦尺寸分析上,當Y/H<0.4時,大p尺度漩渦尺寸會因降雨而減小;
在近水面處,大小尺度漩渦尺寸則會]降雨而增大。

In the literture, the studies of the shallow rain-impactedlow
were limited to the effects of the rainfall intensity. Be-ides
rainfall intensity , the effect of raindrop size and thehannel
roughness were also considered in the current researcho widen
the experimental ranges. The Fiber-optic Laser
Dopplerelocimenty (FLDV) technigue was used to measure the flow
char-cteristics, The flume bottom were covered by glass
particles of 0.85mm and 8mm in diameter. The experiments
includ rainfallituta-tions . All the flow in this study were
the subcritical flow. The objectives of this reaserch were to
study the mean velo-ity profiles, the two-dimensional
turbulence intensities, tress distributions,Darcy-Weisbach
friction factor, power nd macroscales and microscales of the
eddy. Besides,models of istributions of turbulence
intensities for both the longitudinalnd vertical directions
were proposed based on the rain fall data.egression equations
were also derived for the prediction of theean and standard
deviation of the Reynolds stress near the flumeottom. The
experments showed that when the bed slope the whole depth he
flow was easy to be penetrated by the raindrops if the ratio
ater depth to raindrop H/d<2, The flow depth was not easy to
be trated if H/d>3. For rough bed with S>0.5%, if H/d<<1.5,
the flow asy to be penetrated; and if H/d>2.5, the flow was
not easy to beenetrated. Two kinds of turbulence intensity
distributions wereroposed and can be applied depending on
whether the flow depth o be penetrated or not. On the other
hand, when the bed slopencreased, the effect of rainfall on the
vertical turbulence ity decreased. When the bed slope was
equal to 0.1%, the nd vertical dimensionless turbulence
intensities became nearly alues of 2.0 and 1.0, respectively.
URI: http://hdl.handle.net/11455/13735
Appears in Collections:土木工程學系所

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