東沙環礁波浪與水流之數值模擬

Numerical Modeling of Waves and Currents in Dongsha Atoll

林義豪(Yi-Hao Lin)

指導教授 ： 蘇仕峯

淡江大學/工學院/水資源及環境工程學系碩士班/碩士(2018年)

https://doi.org/10.6846/TKU.2018.00964

摘要

東沙環礁處於颱風通過較為頻繁之區域，經常受到劇烈波浪影響，然而環礁內潟湖水域受到環礁遮蔽致使波浪不易直接入侵，但根據現場觀測顯示潟湖之波浪在強風作用產生之能量仍不容忽視。因此，本研究主要在探討東沙環礁潟湖之波浪與水流受風作用力之特性。本研究利用NearCoM波流耦合模式進行模擬計算，並以外海浮標與環礁內現場觀測資料，率定出珊瑚礁環境之碎波參數和底床摩擦係數，進而比較各方向之波向與風向作用下，有風與無風時波浪與水流於環礁潟湖內之發展，由模擬結果發現，在風的作用下波浪發展會非常顯著，隨著風域越長則波浪發展越高。風作用力會增強水流流速並在潟湖內形成渦流，此外，水流會經由南北水道流出潟湖與外海的水體交換。

關鍵字

東沙環礁 ； 波浪 ； 水流 ； NearCoM ； 風作用力

並列摘要

Dongsha Atoll is located in the northern of the South China Sea. Because of its location at paths of typhoons, effects of violent waves on the reef are significant. Waves inside the atoll lagoon are not energetic because offshore waves are sheltered by the atoll reef. However, field observations have indicated that wave energy in the lagoon is considerable. The aim of this study is to understand wave characteristics in the atoll lagoon with wind forcing. A wave-current coupling model, NearCoM, is used to simulate waves and currents on the atoll. Two important physical parameters for wave breaking and bottom friction are calibrated by available field observations. With calibration, wave and current fields are studied by the model experiments with and without wind forcing. Characteristics of waves and currents in different wind directions are studied as well. Model results show that the generation of lagoon waves is depend on the length of fetch inside the lagoon. Developing waves are significant in the atoll lagoon. Additionally, wind forcing increases the speed of currents and generates circulations. Lagoon water exchange with sea through the two reef channels. Wind forcing could increase the water exchange processes.

並列關鍵字

Dongsha Atoll ； Waves ； Currents ； Wind forcing ； NearCoM

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