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研究生:陳木祥
研究生(外文):Mu-Shuang Chen
論文名稱:在波浪作用下沙灘剖面變化之數值模擬
論文名稱(外文):A Numerical Simulation of Profile Changes on a Sloping Sandy Beach
指導教授:林意楨林意楨引用關係
指導教授(外文):I-Chen Lin
學位類別:碩士
校院名稱:淡江大學
系所名稱:水資源及環境工程所
學門:工程學門
學類:環境工程學類
論文種類:學術論文
論文出版年:1995
畢業學年度:83
語文別:中文
論文頁數:57
中文關鍵詞:溯升回降向離岸漂沙沙灘剖面
外文關鍵詞:run-upback-washon-offshore sedimentbeach profile
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本文為探討在波浪作用下,因向離岸漂沙運移所造成的斜坡沙灘剖面之變
化,以不同的波浪特性和沙灘坡度分析其對沙灘地形變化、輸沙量和輸沙
率之影響。本研究對於波浪在斜坡上溯升之模擬使用有限振幅淺水波理論
;當溯升至最高點後,隨即以自由落體觀念和質量守恆定律模擬波浪回降
之流況; 在外海邊界上之入射波除了波頭 (bore)型式外,本研究亦考慮
微小振幅波型式。對於輸沙量計算本研究採用 Bagnold 總輸沙量公式,
並考慮地形之局部坡度之影響;且假設在邊界向外海之下一格點為地形沖
淤平衡點。為了模擬波浪不斷進入沙灘斜坡之情形,本研究應用疊加原理
來模擬,並考慮地形變化後流況因發生水躍、底床抬高和淤積地形水流無
法通過時之變化。從其模擬結果可知:以自由落體運動模擬波浪回降,其
效果似乎不錯;入射波為微小振幅波型式與實驗結果較符合;原始沙灘坡
度亦是影響沙灘剖面變化的重要因素。在外海邊界之下一個格點本研究假
設為沖淤平衡點,經模擬沙灘地形變化之結果,在原始灘線至外海邊界沖
刷形成U字型地形。入射波為波頭型式在緩坡沙灘時,在原始沙灘以上會
淤積成沙洲(bar) 。入射波為微小振幅波型式,若週期短、波高大和原始
沙灘坡度緩,在原始灘線處較易沖刷成沙洲地形。
This study is to develope a numerical simulation of the
profile changes on sloping sandy beach due to on-offshore
sediment transport under continuous wave actions. This
research has discussed the topographic variation of beach,
changes of sediment volume, and sediment transport rate with
respect to the effects of wave characteristics and the beach
slope. Wave run-up on sloping beach is simulated by the
finite-amplitude shallow-water wave thoery. When the run-up
reaches the maximum level, the back-wash is then simulated by
the free-falling motion afterward. The concept of mass
conservation is also considered. We have considered two
forms of seaward boundary conditions, bore form and the
small amplitude wave form. The sediment transport quantities
are calculated by the Bagnold''s formula, and the local slope
changes due to the sediment movement have been taken into
consideration. The null point is assumed to be at the grid
point next to the seaward boundary seawards. To simulate the
continuous incident waves, the superposition method is
adopted. Owing to the profile changes, this study considers
three flow situations which are hydraulic jump, flow through
humpy bed, and no flow condition. The results of back-wash
simulated by the free-falling motion are fine. The outcomes of
using the small amplitude wave form at the seaward
boundary have better agreement compared with the
experimental results. The effect of the original beach slope is
another important factor to the beach profile changes.
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