• 作者： 侯和雄
• 作者服務機構： 國立臺灣海洋學院河海工程研究所
• 中文摘要： 本研究包括(一)波浪作用下傾斜底床上剪力值之理論推導與其實驗證明。(二)砂粒起勁水深與波性之關係。 考慮及傾斜底床上之重力分量後，根據微小振幅波理論可解出底床剪力值之理論式 。(Hou＆ Lee, 1980)，在邊界厚度 相當大時， 值成週期變化。而根據實驗顯示， =2.4/(方程式無法摘錄)=2.4/β 時，( ) 之理論值與實驗值頗為相近。 由實驗資料顯示，在波浪作用時，砂粒起動水深與波性之關係如下： 粒徑小於0.5 mm時為(方程式無法摘錄) 粒徑大於0.5 mm時為(方程式無法摘錄) 此處 及 分別為流體與砂粒之密度， 為底床附近之最大流速，d 為底床附近水分子軌跡之振幅，D 為平徑粒徑， 為波浪之角頻率， 為流體之運動黏性 (kinematic viscosity)。
• 英文摘要： The former scholars Bagnold (1946) andManohar (1955) studied the threshold of sedimenton oscillating plate under the unsteady flow,also Rance and Warren (1968) investigated thecritical depth of sediment movement by oscilla-ting flow. From these tests, the flow patternsin the boundary layer were easily determined,but these situations are quite different from thatare under wave action. In order to find out thethreshold of sediment under wave action forcoastal zone, the objective of this project is tomeasure the shear stress and the velocity profilein the boundary layer in the hydraulic labora-tory. From the experimental results, the bound-ary layer is easily determined by the conditionof different wave period and height, and there-fore the threshold of sediment is determined. By varying wave condition, the proceduresincluding two tests are described as follows:(1) testing the threshold of sediment of differentsize under wave action, (2) by using the displace-ment gauge and shear plate to measure the bot-tom shear stress under wave action. Then fromthe results of (2), the relation between wavecharacteristics (wave period and height) and theflow pattern in the boundary layer is determined.By combining this result with the test results of(1), empirical formula and the monograph amongparameters of grain size, water depth which thesand moves and moves, and the wave charac-teristics (wave period and height) are found out.The research results could be applied to practicalcases, such as to find out the littoral process ofcoast, to determine sediment transport rate alongthe active sandy coast, etc.
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