Research Associate, Case Western Reserve University
A combination of advanced testing method and analytical solution to solve practical problems
Wind energy is one of the most promising renewable energy sources, and recent focus has been on offshore wind development projects. The sustainable development of offshore wind energy requires thorough investigations of technological issues. The substructure, which acts as the natural link between the technology and the environment, is a critical topic for the offshore wind industry. The application of traditional offshore wind foundations is limited by the ability to adapt to different water depths. Therefore, innovative foundations types are proposed and investigated in my research, such as suction bucket foundation and hybrid monopile-friction wheel foundation. They are designed with the purpose of covering a larger range of water depths at a lower cost. The main load characteristics of offshore wind turbines are large lateral loads and overturning moments, and earthquake loads for wind farms built in seismically active areas. Therefore, lateral and seismic load conditions are the main concerns in this research. A series of centrifuge tests were performed to investigate the seismic and lateral behaviors of the innovative foundations for offshore wind turbines. Analytical methods were demonstrated and verified with the experimental results. Numerical simulations were also conducted to investigate the soil-structure interactions. The research outcomes are expected to help predict field performances of offshore wind turbines and provide design references for future projects.
Abstract: In this paper, the slamming coefficients on local members of a jacket structure under plunging breaker are studied based on numerical simulations. A 3D numerical model is used to investigate breaking wave forces on the local members of the jacket structure. A wide range of breaking wave conditions is considered in order to get generalized slamming coefficients on the jacket structure. In order to make quantitative comparison between CFD model and experimental data, Empirical Mode Decomposition (EMD) is employed for obtaining net breaking wave forces from the measured response, and the filtered results are compared with the computed results in order to confirm the accuracy of the numerical model. Based on the validated results, the slamming coefficients on the local members (front and back vertical members, front and back inclined members, and side inclined members) are estimated. The distribution of the slamming coefficients on local members is also discussed.
Pub.: 06 Apr '17, Pinned: 27 Jun '17
Abstract: An integrated finite element model(FEM)of offshore wind tower-foundation-soil is established by ABAQUS, where a large-scale composite bucket foundation with seven compartments inside is applied to supporting the upper wind tower. The dynamic response of the structure-foundation system is studied under three seismic waves with the same peak ground acceleration of 0.035g. It can be seen that the dynamic response increases at the beginning with the structure height, then it decreases because the structural damping increases due to the mass effect of the upper wind turbine generator system. It is shown that the anti-liquefaction capacity of the soil inside and underneath the foundation is improved owing to the high overburden pressure of the upper structure and the constraint effect of the bucket skirt and subdivisions. Moreover, the liquefaction resistance of the soil inside the middle compartment is improved to a higher degree than that inside the side compartments.
Pub.: 06 Aug '16, Pinned: 27 Jun '17
Abstract: Wind power has made rapid progress and should gain significance as an energy resource, given growing interest in renewable energy and clean energy. Offshore wind energy resources have attracted significant attention, as, compared with land-based wind energy resources, offshore wind energy resources are more promising candidates for development. Sea winds are generally stronger and more reliable and with improvements in technology, the sea has become a hot spot for new designs and installation methods for wind turbines. In the present paper, based on experience building offshore wind farms, recommended foundation styles have been examined. Furthermore, wave effects have been investigated. The split installation and overall installation have been illustrated. Methods appropriate when installing a small number of turbines as well as those useful when installing large numbers of turbines were analyzed. This investigation of installation methods for wind turbines should provide practical technical guidance for their installation.
Pub.: 23 May '10, Pinned: 27 Jun '17