Transformed-FNV: Wave forces on a vertical cylinder - A free-surface formulation
Transformed-FNV: Wave forces on a vertical cylinder - A free-surface formulation
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Transformed-FNV：垂直圆柱体上的波浪力 - 自由表面公式
DOI：
10.1016/j.coastaleng.2024.104454
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发表时间：
2024
影响因子：
4.4
通讯作者：
Taylor P
中科院分区：
文献类型：
--
作者：
Taylor P
现有的立式穿面圆柱受力模型需要从海床到自由水面的水深积分来确定总线内力。然而，获取水面下完整的波浪运动学剖面是一项重要的计算任务。我们重新审视了著名的FNV理论的有限水深版本（Kristiansen和Faltinsen， 2017），并提出了一个转换版本，该版本仅用自由表面的完全非线性波动特性来表达总力。这种新颖的变换- fnv （T-FNV）公式精确地处理了莫里森惯性项，并以缓慢变化的动能类型项为假设近似其余两个对流导数类型项。我们利用从完全非线性数值模拟中获得的波动运动学来评估这种转换对原始公式的准确性。提出了两种不同输入特性的T-FNV公式。第一种公式使用自由表面的完全非线性波动运动学特性，而完全近似的T-FNV公式只需要在柱的位置测量或计算的非线性自由表面高程时程，但没有它。与原始的FNV模型相比，两种T-FNV公式对深水和浅水情况下的波浪力都具有良好的准确性。新的T-FNV公式还表明，与自由表面位移相比，高次谐波在预测力时程中的作用更大，以及在非线性力计算中使用精确的高次谐波剖面的重要性。
Existing force models for a vertical surface-piercing cylinder require water depth integration from the seabed to the free surface to determine the total inline force. However, acquiring the full wave kinematics profiles beneath the water surface presents a significant computational task. We revisit the finite water depth version of the well-known FNV theory (Kristiansen and Faltinsen, 2017) and propose a transformed version that expresses the total force solely in terms of the fully nonlinear wave properties at the free surface. This novel Transformed-FNV (T-FNV) formulation treats the Morison inertia term exactly and approximates the remaining two convective-derivative type terms with an assumption of slowly varying kinetic energy type terms. We evaluate the accuracy of this transformation against the original formulation, using wave kinematics obtained from fully nonlinear numerical simulations. Two T-FNV formulations are proposed with different input properties required. The first formulation uses the fully nonlinear wave kinematic properties at the free surface, whereas a fully approximated T-FNV formulation requires only the nonlinear free-surface elevation time history measured or calculated at the position of the column but in its absence. Both T-FNV formulations demonstrate good accuracy for wave forces for both deep and shallow-water cases against the original FNV model. The new T-FNV formulations also show the increased role of higher harmonics in the predicted force time histories when compared to those in the free-surface displacement, and the importance of using accurate higher order harmonic wave profiles in nonlinear force calculations.