Abstract Mangrove forests can significantly attenuate tsunami waves and thus play an important role in coastal protection. As a first approximation, the problem is modeled utilizing solitary waves impinging on emergent/submerged rigid cylinders. A three-dimensional (3-D) numerical model using cyclic boundary conditions was developed based on the IHFOAM solver to investigate the effects of wave nonlinearity and vegetation configuration on the solitary wave attenuation. The numerical model was established based on the Reynolds Averaged Navier-Stokes (RANS) equations combined with the standard k – ω shear stress transport (SST) turbulence model and the volume of fluid (VOF) surface capturing schemes. The results indicate that different patterns are found in terms of flow field characteristics (velocity and turbulent kinetic energy) and forces exerted on the cylinders for various wave nonlinearity and vegetation configuration, which helps to better understand wave dissipation mechanism induced by vegetation. Different from the bulk drag coefficient derived by the conventional wave dissipation models, the direct force method was applied to quantify the time-varying and period-averaged drag coefficients (CD) of individual cylinders. The time-varying CD associated with maximum force and local velocity is defined as the representative CD, for comparison with the period-averaged CD in detail. Besides, by considering the submergence ratio, new generic CD formulas are proposed as functions of the modified Reynolds number (Re) and Keulegan-Carpenter number (KC) for illustrating the CD dynamics under solitary wave conditions. Finally, a preliminary comparison between the proposed CD formulas and existing formulas are given to reveal the intrinsic CD law, which may lead to improved understanding and modeling concerning wave-vegetation interaction.

中文翻译：

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基于3-D RANS模型的刚性植被引起的孤立波衰减和阻力数值研究

摘要 红树林可显着减弱海啸波，在海岸保护中发挥重要作用。作为第一个近似值，该问题是利用撞击出水/水下刚性圆柱体的孤立波来建模的。基于 IHFOAM 求解器开发了使用循环边界条件的三维 (3-D) 数值模型，以研究波浪非线性和植被配置对孤立波衰减的影响。数值模型是基于雷诺平均纳维-斯托克斯 (RANS) 方程结合标准 k – ω 剪切应力传输 (SST) 湍流模型和流体体积 (VOF) 表面捕获方案建立的。结果表明，在流场特征（速度和湍流动能）和施加在圆柱体上的各种波浪非线性和植被配置的力方面发现了不同的模式，这有助于更好地理解植被引起的波浪耗散机制。与传统的波浪耗散模型推导出的体积阻力系数不同，直接力法用于量化单个圆柱体的时变和周期平均阻力系数（CD）。与最大力和局部速度相关的时变 CD 被定义为代表性 CD，以便与周期平均 CD 进行详细比较。此外，通过考虑淹没比，提出了新的通用 CD 公式作为修正雷诺数 (Re) 和 Keulegan-Carpenter 数 (KC) 的函数，用于说明孤立波条件下的 CD 动力学。最后，对所提出的 CD 公式与现有公式进行初步比较，以揭示内在的 CD 规律，这可能会提高对波-植被相互作用的理解和建模。