全非线性波的高阶谱方法

Efficient generation of an accurate numerical wave is an essential part of the Numerical Wave Basin that simulates the interaction of floating structures with extreme waves.computational fluid dynamics(CFD)is used to model the complex free-surface flow around the floating structure.To minimize CFD domain that requires intensive computing resources,fully developed nonlinear waves are simulated in a large domain that covers far field by more efficient potential flow model and then coupled with the CFD solution nearfield.Several numerical models have been proposed for the potential flow model.the higher-level spectral(HLS)method presented in this paper is the extended version of HLS model for deep water recently been derived by combining efficiency and robustness of the two existing numerical models–Higher-Order Spectral method and Irrotational Green-Naghdi model(Kim et al.2022).The HLS model is extended for the application of finite-depth of water considering interaction with background current.The verification of the HLS model for finite depth is made by checking the qualification criteria of the generated random waves for a wind-farm application in the Dong-Hae Sea of Korea.A selected wave event that represents P90 crest height is coupled to a CFD-based numerical wave tank for the future air-gap analysis of a floating wind turbine.

浮式海上风力发电机的时域响应结构分析

As the turbine blade size becomes larger for economic power production,the coupling effect between wind turbine and floating substructure becomes important in structural assessment.Due to unsteady turbulent wind environment and corresponding coupled substructure response,time-domain analysis is required by international electrotechnical commission and class societies.Even though there are a few numerical tools available for the time domain structural analysis based on conventional coupled motion analysis with wind turbine,the application of conventional time domain analysis is impractical and inefficient for structural engineers and hull designers to perform structural strength and fatigue assessment for the required large number of design load cases since it takes huge simulation time and computational resources.Present paper introduces an efficient time-domain structural analysis practically applicable to buckling and ultimate strength assessment.Present method is based on‘lodal’response analysis and pseudo-spectral stress synthesizing technique,which makes timedomain structural analysis efficient and practical enough to be performed even in personal computing system.Practical buckling assessment methodology is also introduced applicable to the time-domain structural analyses.For application of present method,a 15-MW floating offshore wind turbine platform designed for Korean offshore wind farm projects is applied.Based on full-blown time domain structural analysis for governing design load cases,buckling and ultimate strength assessments are performed for the extreme design environments,and the class rule provided by Korean Register is checked.