非线性畸形波所致的平台底部砰击载荷及结构响应数值模拟

Numerical Simulations of Impact Loads and Structural Responses of Bottom Decks of Platforms Caused by Nonlinear Freak Waves

基于求解2维N-S方程和流体体积(VOF)法建立数值水槽,采用Peregrine呼吸子解模型进行非线性畸形波的造波,采用2维有限元法对平台下甲板结构离散,并以一种流固耦合算法针对非线性畸形波平台底部砰击进行数值模拟.计算了该砰击问题中非线性畸形波引起的砰击载荷,并揭示了其与相同波高、波长2阶规则波引起砰击载荷的不同.考虑平台下甲板结构为弹性体的结构响应,在平台下甲板结构存在垂向初速度的条件下得到了平台下甲板结构位移时历,并采用快速傅里叶变换(FFT)对频率响应进行了分析.

In order to study the impact on offshore platforms caused by nonlinear freak waves,a numerical wave tank is built,in which the incompressible Navier-Stokes equations are solved,with the free surfaces reconstructed using a VOF method.Nonlinear freak waves based on the Peregrine breather solution are generated.A fluid-structure interaction(FSI)algorithm is used to calculate the structural response of the bottom deck,which is discretized with the finite element method(FEM).The impact loads underneath a platform model are calculated and compared with the ones caused by the 2 nd-order regular waves with the same wave lengths and heights to reveal the unique features of the impact caused by nonlinear freak waves.The structural response of the bottom deck is calculated using the FSI algorithm and processed with an FFT method to analyze the wetted vibration.Additionally,the influence of the vertical initial velocity is considered during the structural response simulations.