The Influence of Strong Nonlinear Waves on the Mono-pile Offshore Wind Turbine Foundation during the Breaking Process

Abstract

In this thesis the computational fluid dynamics (CFD) numerical method is used to solve fluid mechanics governing equations and a flow field simulation The influence of the interaction between the strong nonlinear waves of tri-chromatic waves and the mono-pile offshore wind turbine (OWT) foundation is discussed We use the finite volume method (FVM) as a numerical solution for the discrete solution and we also solve the problem of two-phase flow using the volume of fraction (VOF) method And the viscous flow problem between the fluid and the wall surface of the mono-pile is solved using the Reynolds-average Navier-Stokes equation (RANS) and the RNG k-ε turbulent model In addition regarding wave conditions we realize the effect of nonlinear wave group interaction wave modulation wave evolution and run-up height of nonlinear wave trains for a mono-pile foundation The wave condition of the tri-chromatic wave consists of one main frequency and two sub-frequencies and it concerns about eight kinds of different non-dimensional modulation factor (δ ?) situations In this study except for the horizontal force of the Morison's semi-empirical formula estimating fluid action fast Fourier transform (FFT) is used Hilbert-Huang transform and empirical mode decomposition (EMD) are also applied for analyzing the energy spectrum in the time domain in order to decompose the total force into quasi-static force dynamic force and slamming force which makes the wave load discussion have more accurate results regarding ocean engineering areas and it also can help the development of offshore wind turbine risk assessment in the future

Date of Award	2019
Original language	English
Supervisor	Yu-Hsien Lin (Supervisor)