Laboratory Study of Integrated Wet-Towing of a Triple-Bucket Jacket Foundation for Far-Offshore Applications

Abstract

As a form of clean and low-carbon green energy, offshore wind power occupies an important position in the global energy structure. With the rapid development of the wind power industry, wind power projects gradually develop from offshore to far-offshore sea areas. The multi-bucket jacket foundation is a considerable foundation type for far off-shore projects, but high installation costs involving ship transportation with parted components and field installation has significantly hindered its wide application. In this study, based on a 6.7-MW triple-bucket jacket foundation (TBJF) project of a deep-sea wind farm in China, a new integrated wet-towing method of “jacket + triple-bucket foundation” composite structure was proposed, which is suitable for far long-distance transportation of far-offshore applications. The static-model test of both self-stability and wet-towing stability was conducted. Based on the test and the numerical results, the natural period of the foundation for different draft depths in hydrostatic water and the stability for different eccentric loads were first evaluated. Then, the effects of different wet-towing modes and sea conditions on the stability of the TBJF were investigated. Finally, the optimal wet-towing mode and applicable sea conditions for the TBJF structure were proposed.

Numerical simulations of towing a jacket foundation with triple buckets

“…To validate the developed time-domain model and the WAMIT solutions with the modified NEWMODES, comparisons were made with the available experimental data in the literature. Although the relevant published data is not many so far, fortunately, we found that Yan et al (2021) [26] recently reported their experimental data which was therefore chosen in the numerical validations. In addition to the data in [26], more experimental data of their research work (obtained from the master dissertation [32]) was also employed in this work, which includes not only the stable towing stage but also the initial towing process.…”

“…In this section, we first briefly introduce the experiments of [26] and then show the comparisons with the numerical solutions of the present time-domain model and the modified version of WAMIT. Following the numerical validations, more details of wet towing of suction bucket jacket, which may be to some extent challenging for direct experimental measurements, will be shown via time-domain simulations.…”

“…Recently, wet towing of a floating structure with suction buckets in waves has been studied due to its engineering significance [17][18]. Guo et al (2021) [19] analyzed the wet towing process of a jacket foundation with four suction buckets by model tests and numerical simulations. Ding et al (2020; 2022) [20][21] studied a composite bucket and found that the compartment pressure changes are small during towing process.…”

“…Hence, a numerical model which can solve 9-DoF motion equations in time domain is established, where the hydrodynamic coefficients as inputs are computed by the WAMIT® code (with extensions to the subroutine NEWMODES). Then, numerical validations of the developed model are carried out against available experimental data [26] under various towing conditions. On this basis, numerical analysis is further carried out to shed insights into the towing problem of air-cushion supported floating structures and provide guidance to engineering practice.…”

“…It was reported in [26] that a series of laboratory model tests on wet towing were carried out in the wave tank at Tianjin University. Figure 7 was taken from their paper, which shows the main experimental setup and the suction bucket model.…”