Abstract Marine structures are typically sensitive to the direction of wind and waves, especially in extreme metocean conditions. The extreme metocean conditions and their associated predicted directions are not easily reachable from traditional design methodologies. In this research, the most probable combinations of different extreme metocean conditions along with their associated direction are predicted for the HyWind Scotland wind farm, Scotland. To achieve this, the Hierarchical Bayesian Modeling approach is applied to define the Joint Probability Distribution Function (JPDF) of four combinations of metocean parameters, including wave direction, wind direction and wind-wave misalignment. The data is provided by the ERA-Interim dataset in 40 years (1979–2018). The JPDFs are composed of a marginal PDF of directional variables (a mixture of von-Mises Fischer distributions) and two conditional JPDFs which are defined to satisfy the periodicity and positivity of distribution parameters. Then, applying the Inverse First-Order Reliability Method (IFORM) to the JPDFs, the Environmental Contours (ECs) for four sets of metocean data are developed. The results show that extreme values obtained from ECs, including directional variables, are higher than the values of traditional linear ECs. The maximum 50-year extreme value of wind speed from the JPDF of wind direction, wind speed and wave height is 2 m/s higher than the same extreme extracted from the JPDF of wind speed, wave height and period. Another important observed point is that the direction at which the extreme of metocean parameters occurs is quite different from their dominant direction of wind rose or the most probable direction of their probability density function. According to the results, it seems for direction-dependent structures; the application of this method may lead to a more realistic presentation of joint occurrence of linear and directional metocean parameters.

中文翻译：

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海洋结构分析和设计中极端气象海洋条件的方向依赖性

摘要 海洋结构通常对风和波浪的方向很敏感，尤其是在极端的海洋气象条件下。传统的设计方法不容易达到极端的海洋气象条件及其相关的预测方向。在这项研究中，为苏格兰 HyWind 苏格兰风电场预测了不同极端气象海洋条件及其相关方向的最可能组合。为实现这一目标，应用分层贝叶斯建模方法来定义四种气象海洋参数组合的联合概率分布函数 (JPDF)，包括波浪方向、风向和风浪错位。数据由 ERA-Interim 数据集提供 40 年（1979-2018）。JPDF 由方向变量的边际 PDF（von-Mises Fischer 分布的混合）和两个条件 JPDF 组成，这些 JPDF 被定义为满足分布参数的周期性和正性。然后，将逆一阶可靠性方法 (IFORM) 应用于 JPDF，开发了四组气象海洋数据的环境等值线 (EC)。结果表明，从 ECs 获得的极值，包括方向变量，高于传统线性 ECs 的值。风向、风速和波高JPDF的50年最大风速极值比风速、波高和周期JPDF提取的相同极值高2 m/s。另一个重要的观察点是，气象海洋参数出现极值的方向与它们的主导风升方向或其概率密度函数的最可能方向有很大不同。根据结果​​，似乎是方向相关的结构；这种方法的应用可能会更真实地呈现线性和定向气象海洋参数的联合出现。