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研究生: 蘇胤銘
Su, Ying-Ming
論文名稱: 以無網格非靜水壓淺水波方程式模擬波浪溯升
A meshless non-hydrostatic shallow water equation model for wave runup
指導教授: 蕭士俊
Hsiao, Shih-Chun
學位類別: 碩士
Master
系所名稱: 工學院 - 水利及海洋工程學系
Department of Hydraulic & Ocean Engineering
論文出版年: 2022
畢業學年度: 110
語文別: 中文
論文頁數: 53
中文關鍵詞: 無網格法淺水波方程式孤立波
外文關鍵詞: meshless method, shallow water equations, solitary wave
相關次數: 點閱:68下載:6
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  • 在工程上經常使用淺水波方程式來模擬淺水波問題。在自然界的水體在水平方
    向的運動較垂直方向更為重要且實務上較為關注水平方向流動的趨勢,因此將複雜
    的三維問題簡化為二維,並且假設壓力在垂直方向為線性分布(即不考慮波浪所引致
    的壓力變化,僅考慮水體所產生的靜水壓) 可推得淺水波方程式。
    若上述之假設符合實際之物理現象,以淺水波方程式為控制方程式輔並以數值
    方法建立一套運算模式,運算所得之結果應當貼近實驗結果與數學理論;但卻發現
    以淺水波方程式模擬孤立波於水平底床的傳遞,會導致孤立波於傳遞過程出現波形
    向前傾倒與不對稱的現象,而且在傳遞中孤立波的波峰亦會有逐步遞減的情況,與
    數學上所描述的對稱波形並不相同。
    本研究以Wu et al. (2021) 的研究作為基礎,以非靜水壓淺水波方程式(nonhydrostatic
    shallow water equations) 為控制方程式並基於無網格數值方法(meshless
    method) 為數值方法,再將數值模式加入乾溼點演算法(wet-dry algorithm) 使得模式
    得以模擬溯升的物理現象,並以四個案例來驗證當前模型之結果。
    案例一,使孤立波通過水平底床來驗證模型的穩定性,目的在於觀察孤立波的
    波形有無傾倒、波峰有無下滑,並將模式的結果與Goring and Raichlen (1980) 解析解
    進行比對。
    案例二,將從邊界生成規則波,並參考Madsen (1971) 所推得規則波的邊界速度
    帶入本模式左側之造波邊界,將所得自由液面結果與Madsen (1971) 實驗結果與Wu et
    al. (2021) 的數值結果進行比對。
    案例三,參考Grilli (1997) 的地形配置使孤立波通過地形變化,並將本模式計算
    所得之自由液面結果與Grilli (1997) 的波高計資料做驗證。
    案例四,使孤立波溯升於一陡峭斜坡(1:2.75),將自由液面時序資料與Zelt
    (1991) 的波高計結果作驗證,並將本模式的溯升過程和實驗比對。

    This paper developed a numerical method based on the non-hydrostatic shallow-water equation to simulate several wave problems. In previous studies, the hydrostatic assumption was broadly applied to the shallow-water-equation, but the results were usually not satisfying. The reason for the errors is that the dispersion terms are ignored in the equations, so it induced the phenomenon of wave inclined or asymmetry. Therefore, this study divided the pressure into hydrostatic and non-hydrostatic terms to optimize the simulation. In addition, this research applied the weighted-least-squares meshless method to approximate the spatial derivatives. To validate the stability and accuracy of the present model, four benchmark problems are demonstrated in this study. The computed results can not only coincide with the experimental data but also save a lot of computation time.

    摘要i Abstract ii 英文延伸摘要iii 誌謝xiii 目錄xiv 圖xvi 符號表xviii 第一章. 緒論1 1.1 研究動機與目的 1 1.2 文獻回顧 2 1.2.1. 非靜水壓淺水波方程式 2 1.2.2. 無網格數值方法 3 第二章. 理論基礎4 2.1 控制方程式 4 2.2 自由液面邊界條件 7 2.3 底床邊界條件 7 2.4 z 方向的平均速度 7 2.5 側向邊界條件 8 2.6 初始條件 8 第三章. 數值模式9 3.1 模式簡介 9 3.2 局部近似(local approximation) 9 3.3 時間域的離散 11 3.3.1. 預測 11 3.3.2. 修正 12 3.4 數值平滑 13 3.5 乾溼點演算法(wet-dry algorithm) 14 3.5.1. 乾溼點的判斷 14 3.5.2. 鄰近乾點的溼點(adjacent wet node) 15 3.5.3. 虛魅水位(fictitious water level) 15 3.5.4. 模式流程圖16 xiv 第四章. 模式驗證與結果18 4.1 孤立波在水平底床傳遞 18 4.1.1. 模式概述 18 4.1.2. 模式配置 18 4.1.3. 驗證結果 19 4.2 規則波在水平底床傳遞 23 4.2.1. 模式概述 23 4.2.2. 模式配置 24 4.2.3. 驗證結果 24 4.3 孤立波通過地形變化 26 4.3.1. 模式概述 26 4.3.2. 模式配置 26 4.3.3. 驗證結果 27 4.4 孤立波溯升 29 4.4.1. 模式概述 29 4.4.2. 模式配置 29 4.4.3. 驗證結果 30 4.4.4. z 方向的平均速度W 34 第五章. 結論與建議41 5.1 結論 41 5.2 建議 42 參考文獻43 Appendix A. 非靜水壓淺水波方程式45 A.1 連續方程式 45 A.2 x 方向動量方程(momentum equation in x-direction) 46 A.3 z 方向動量方程(momentum equation in z-direction) 49 Appendix B. z 方向平均速度W 的理論解 51 Appendix C. 動水壓Q 的理論解 53

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