本論文研究目的，係針對由成大水工試驗所(2000s) 所發展之海岸開發與管理模式(Coastal Reclamation and Management model，簡稱CRM模式)，探討近岸流系統中各影響因素之敏感度與重要性，並依據數值實驗，在近岸流場數值模擬上給予建議。CRM模式為一平面二維數值模式，流場主要控制方程式為淺水波方程式，波浪場部分則為緩坡方程式；其中波浪對流場之效應係以輻射應力呈現於淺水波方程式中。本模式之最終目的，係模擬並探討近岸漂砂與底床地形變遷之問題，然而卻發現在近岸流場與波場存在不可忽略之誤差，因此本研究期望可以針對此一問題作探討與改善之建議。

原版本之CRM模式中之波浪場係採用RCPWave (Ebersole et al., 1986)求解，然而，根據Maa et al.(2000) 以及Kirby (2000)之研究與探討，可得知RCPWave雖計算效率高，但在波浪非線性較強之情況下，卻會導致明顯不理想之計算結果，除此之外，本研究亦發現，REF/DIF 1於數值計算上相較於RCPWave更加穩定。因此，為兼顧效率與精確度，本研究改採用REF/DIF 1 (Kirby and Dalrymple, 1994)，於CRM模式中求解波浪場。

由於現地流場模擬過於複雜，本研究首先針對前人已進行之近岸流場之實驗進行驗證與探討。過去數十年中有許多相關的研究，Visser(1991)針對文獻中不同之沿岸流相關量測實驗配置做一整理與探討，並重新設計實驗配置與量測方法，以達到足夠之精確度供研究使用。Visser(1991)之研究成果在近年中被廣泛應用於相關問題之探討，因此本研究亦採用其實驗數據做為數值試驗探討對象。

此數值試驗結果，將依據由敏感度分析所得之建議參數設定，呈現於本研究之結果與討論中。經本研究的數值試驗可知：CRM模式配合REF/DIF 1以及Roller模式時，可得到較理想的結果；然而，在底床糙度較大時(如礫石灘)，本模式數值結果仍不理想，本研究認為此部分是波浪模式中，針對底床糙度造成之能量損失考量不足所導致。倘若可以進行更進一步之研究，首要當是更深入探討較大之底床糙度對於波浪以及碎波表面滾動(Surface rollers)之影響，並嘗試針對現地資料進行驗證與分析。最後，期盼本研究可於未來被應用於建立更準確的近岸漂沙、海底地形變遷模式中。

This study presents the sensitivity analyses and some corresponding findings in two-dimensional near-shore current simulation based on the Coastal Reclamation and Management model (CRM model) developed by THL, NCKU, whose governing equations of current fields are shallow water equations. The main purpose of this model was simulating near-shore sediment transportation and bed morphology evolution; however, non-negligible errors were found to exist in the computed near-shore current field. This might lead to meaningless predictions of sediment transportation and bed morphology evolution in that the current-field result plays a significant role in sediment transportation. Consequently, we commenced to devote to the investigation of near-shore current system based on CRM model.

The focused topics include wave models, wave breaking criteria, bed resistance evaluation, bottom friction formulas, eddy diffusion, and surface roller. For wave models, two widely used models including RCPWave and REF/DIF 1, both of which based on mild-slope equation, were taken into account. The one installed in CRM model originally was RCPWave; nevertheless, referred to Maa et al. (2000) and Kirby (2000), REF/DIF 1 was stated to be able to capture the wave variation accurately rather than RCPWave did especially when the nonlinearity is important. In addition, RCPWave was found to be less stable than REF/DIF 1; hence the original CRM model was modified to be coupled with REF/DIF 1 instead of RCPWave in present study.

Further discussions and analysis were carried out after the comparison of wave models. Since we focus on the impact factor analyses in present study, the chosen experimental study or measurements should be determined carefully. Visser (1991) gave the comparison of longshore current experiments in the past and proposed an improved one in his investigation, which has been widely used and applied then. In consequence, longshore current measurements by Visser (1991) is adopted in present investigation for model verifications.

Finally, computed results, discussions, suggestions and conclusions would be presented in the last two chapters of present study. The modified CRM model coupled with REF/DIF 1 and surface-roller model leads to great results in current field. Yet, it was found that the modified CRM model still could not perform well against gravel beaches, which should be attributed to the frictional energy loss estimation in wave models. As for the future works, this issue should have the top priority. Then, outcomes and conclusions of present study are expected to be applied to the field investigation and, eventually, the sediment transportation and bed morphology.

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