海岸植栽與柔性消波結構常被用於減緩波浪衝擊，在水流作用下會產生彎曲與擺動，使波浪、流場與結構反應之間形成交互影響。為探討孤立波通過柔性結構物時的交互作用，本研究以潛沒式直立圓柱作為簡化模型，探討孤立波通過剛性與彈性圓柱時之自由液面變化、水平受力、結構位移與尾流發展。數值模型採用 OpenFOAM 結合 solids4Foam 建立三維流固耦合數值水槽，流體部分以 RANS 方程式搭配 k−ω SST 紊流模式求解，並利用 VOF 方法捕捉自由液面；彈性圓柱則透過固體控制方程式計算結構變形，並以 ALE 動態網格與 Aitken 動態鬆弛法處理流固耦合過程。
本研究首先以均勻流通過有限長圓柱案例和文獻比對，驗證數值模式對圓柱阻力與三維尾流特徵之預測能力。接著針對孤立波通過剛性圓柱案例，將自由液面、水平受力、速度場與渦度場結果與實驗結果進行比對。最後以孤立波通過彈性圓柱案例，比較數值模擬與實驗量測之自由液面、速度場及渦度分布，以確認本研究流固耦合模型於彈性結構問題中之適用性。
本研究接著比較孤立波通過剛性與彈性圓柱時之自由液面、水平受力、結構位移與尾流發展，並探討不同彈性係數對流固耦合反應之影響。結果顯示，結構彈性對整體自由液面傳遞影響有限，主要差異出現在圓柱受力、位移反應與後方尾流結構。相較於剛性圓柱，彈性圓柱之水平受力峰值略低，且位移峰值晚於受力峰值出現。不同彈性係數比較則可得知，彈性係數較低時，圓柱順流向變形與回彈明顯，受力變化維持時間也較長。但渦度分布與三維尾流結構並非單純隨彈性係數降低而增強，而是受到結構變形、回復運動與尾流交互作用共同影響。

This study investigates the interaction between a solitary wave and a submerged vertical cylinder as a simplified model of flexible coastal structures. A three-dimensional fluid–structure interaction model was developed using OpenFOAM coupled with solids4Foam. The fluid field was solved with the RANS equations and the k–ω SST turbulence model, while the free surface was captured using the VOF method. Structural deformation was handled through an ALE dynamic mesh and Aitken's dynamic relaxation method.
The model was validated against finite-cylinder flow data and solitary-wave experiments with rigid and elastic cylinders. The results show that structural elasticity has little influence on the overall free-surface variation, but affects the horizontal force, displacement response, and wake development. The elastic cylinder shows a slightly lower peak force than the rigid cylinder, and its maximum displacement occurs after the force peak. For different Young's moduli, lower stiffness leads to larger deformation and longer force duration, while the wake structure is governed by deformation, recovery motion, and wake interaction.

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