http://scholars.ntou.edu.tw/handle/123456789/14710
標題: | 單一離岸堤背後海岸線變遷之研究 | 其他標題: | Shoreline Changes behind a Single Permeable Breakwater | 作者: | 許泰文 徐立政 張憲國 |
關鍵字: | 離岸堤;Breakwater | 公開日期: | 1996 | 出版社: | 中國土木水利工程學會 | 卷: | 9 | 期: | 3 | 起(迄)頁: | pp. 473-482 | 來源出版物: | 中國土木水利工程學刊 | 摘要: | 往昔學者大多使用一維單線模式預測海岸結構物設置後之海岸線變遷, 但結構物附近之近岸流場具二維性,以一維模式難以描述結構物附近之流 場與漂沙運移特性時,其適用性常受限制。 本文提出單線半海岸線變遷 模式,用以模擬單一透水性離岸堤背後之海岸線變化。文中先引用非定常 緩坡方程式解析波浪折射、繞射、反射及淺化等效應,由波高分佈計算近 岸流場,再結合輸沙濃度推求堤後海岸線變遷。本模式之計算結果亦與前 人之試驗結果相比較,結果顯示預測值與實測值大致相符。本文並探討不 同透過率、離岸距離、波浪條件等因素對堤後海岸線變遷之影響。結果顯 示,不透水之堤體,遮蔽效果較佳,輻射應梯度較大堤後流場較強,較有 利形成堤後沙舌長度或繫岸沙洲;不同離岸距離情況時,堤後沙舌隨離岸 距增加,而在 S/B=1.25 時沙舌已增加幅度已經很小,表示此時為較佳的 擺設方式。其中 S 為離岸距離, B 為離岸堤之寬度。不同波浪條件之情 況下,本文計算結果,隨著深海波高的增大,沙舌長度越長。而較長波浪 週期所產生繞射係數變大而沙舌長度與寬度也隨之變大。Water waves incident on a sandy beach may generate nearshore circulations behinddetach breakwaters, which produce a varying sediment transport field resultingin shoreline changes. Previous one-line models with no flow field are limitedto describe shoreline response to detached breakwaters. A numerical modelincludes three submodels predicting wave field, nearshore currents and shorelinechanges behind a single permeable breakwater is developed in this paper. The mild-slope equation with a combination of refraction diffraction andreflection is solved in the form of hyperbolic approximation. Wave- inducednearshore currents are calculated on the basis of radiation stresses obtainedfrom wave field. Shoreline changes behind a single parallel detached breakwateris predicted from nearshore currents and continuity of sediment transport. Thevalidity of the present model is verified through experiments and reasonableagreements are found. The effects of wave steepness, distance from the shoreline to the breakwaterand porosity on shoreline changes are investigated. Numerical results showthat the ability of a breakwater to shelter water bodies from waves and formsand salient and tombolos decreased with the increase of the porosily. Thesalient grows and advances as the wave height and wave period increases.Sand spits don''t protrude in the case of S/B=1.25 , where S is the offshoredistance and B is the length of the detached breakwater, respectively. |
URI: | https://hdl.handle.net/11296/56dmv6 http://scholars.ntou.edu.tw/handle/123456789/14710 |
顯示於: | 河海工程學系 |
在 IR 系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。