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題名 | 離岸堤對離島式圓形港灣附近波動現象之影響研究=The Influence of Offshore Breakwater on Wave Conditions around an Offshore Circular Harbor |
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作 者 | 岳景雲; 張芷婷; 涂靜宜; 莊世璿; | 書刊名 | 海洋工程學刊 |
卷期 | 17:2 2017.06[民106.06] |
頁次 | 頁65-90 |
分類號 | 443.3 |
關鍵詞 | 圓形港灣; 離岸堤; 波力; 繞射; 複合邊界元素法; Circular harbor; Offshore breakwater; Wave force; Diffraction; Composite BEM; |
語文 | 中文(Chinese) |
中文摘要 | 為了發展離岸港口、能源島及海中城市等離島式結構物時,都需要設置一接駁用港灣以利海上作業,將具有離岸堤保護之圓形開口港灣設置於外海中,其構想是由Hariri Nokob and Yeung (2015)所提出,固定圓形開口角度為120°及相對半徑為a/h=1/3,將離岸堤分別設置在港內、港口附近及港外,並且改變長度,探討離島式圓形港灣之波動現象,並利用複合邊界元素法(CBEM)解析波浪作用在圓形港灣及離岸堤之無因次波力及繞射係數分佈圖,為了驗證模式正確性及可行性,其他學者之數值解作比對,獲得正確且合理結果。本文將探討影響圓形港灣波動現象主要有兩個無因次參數,分別為離岸堤相對長度(l/h)及相對位置(d/h)。數值計算結果顯示:具有離岸堤保護之圓形港灣之無因次波力峰值會比無離岸堤保護時之波力峰值大;而開口圓形港灣在低頻區會有無因次波力峰值發生;如果加上離岸堤設置後,會造成港灣開口角度變小,因此波力峰值不但會增加,而且分佈變得更為尖而窄。 |
英文摘要 | The concepts of offshore structures as offshore port, energy islands, and city in the sea have received considerably much attention. For the convenience of maritime operations, it would be accompanied by constructing a connected offshore harbor. A model of an open harbor with a frontal offshore breakwater in a wave field inspired by the idea of Hariri Nokob and Yeung (2015). In this paper, the influence of offshore breakwater on wave conditions around an offshore circular harbor are investigated. Under the linear wave theory, we solve the problems by using composite boundary element method (CBEM). The accuracy and validity of the present method have been compared to the solution obtained from other numerical results. Excellent agreement has been observed. All numerical results presented are for a relative radius of circular harbor a/h=1/3 with an opening angle fixed 120°. Two parameters including the relative length(l/h) of the offshore breakwater and the distance(d/h) between offshore breakwater and the center of the circular harbor are considered. The dimensionless wave force acting on both open circular harbor and offshore breakwater are explored and discussed. Numerical results also have presented the magnitude of the diffraction coefficient with different wave contidions. The peak value of the dimensionless wave force of open circular harbor with a protected offshore breakwater is larger than without offshore breakwater. The numerical results indicate that a very large dimensionless wave force locate at lower frequency when the harbor is opened. The dimensionless wave force is observed to be much sharper and larger, especially as the opening gets smaller. |
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