Accurate and efficient calculation of all second-order wave load components in six degrees of freedom (6DoF) remains a challenging task, in particular for structures with sharp edges. Based on Gauss theorem, we have tailor-made an efficient method for direct time-domain solvers utilizing, for instance, boundary element methods. Unlike other methods based on momentum conservation or Gauss theorem that require control surfaces, this method only involves integrals on the structure and free surfaces. The accuracy and efficiency of the method are firstly verified for the mean and sum-frequency wave forces on a hemisphere and a truncated vertical cylinder. Subsequently, an application to study the motion responses of a semi-submersible floating offshore wind turbine (FOWT) in focused waves is presented, where experimental results are also available. The results indicate that the proposed method can greatly improve the computational efficiency in accurately predicting second-order loads on offshore structures with sharp edges in direct time-domain solvers. For the FOWT in focused waves, this alternative method is essential in achieving accurate prediction of hydrodynamic responses near the focus time.

中文翻译：

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直接时域模拟中二阶波浪载荷的准确评估


准确有效地计算六自由度 (6DoF) 中的所有二阶波浪载荷分量仍然是一项具有挑战性的任务，特别是对于具有锐利边缘的结构。基于高斯定理，我们为直接时域求解器量身定制了一种有效的方法，例如利用边界元方法。与其他基于动量守恒或高斯定理需要控制面的方法不同，该方法仅涉及结构和自由表面上的积分。首先针对半球和截头立柱上的均频波力和和频波力验证了该方法的准确性和效率。随后，提出了研究半潜式浮​​动海上风力发电机（FOWT）在聚焦波中运动响应的应用程序，并提供了实验结果。结果表明，该方法可以大大提高直接时域求解器中精确预测具有尖锐边缘的海上结构二阶载荷的计算效率。对于聚焦波中的 FOWT，这种替代方法对于实现聚焦时间附近的水动力响应的准确预测至关重要。