High-Level Spectral Method for the Fully Nonlinear Waves

Abstract

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.

Keywords

Fully nonlinear wave / Higher-level spectral / Computational fluid dynamics / Numerical wave tank / Wind-farm / Air-gap