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Title: Integrated numerical model for wave induced seabed response around offshore structures
Author: Lin, Zaibin
ISNI:       0000 0004 6346 4558
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2017
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Seabed stability in the vicinity of those offshore structure, which has been one of the particular concerns in engineering practice, can be compromised by the action of energetic waves. This project investigates the mechanisms of wave-induced soil response and liquefaction in a porous seabed near offshore structures. For this purpose both 2-Dimensional (2-D) and 3-Dimensional (3-D) integrated Wave-Seabed-Structure Interaction (WSSI) models have been developed within the project. They were used to simulate the effect of nonlinear wave-structure interaction on dynamic soil response in the neighbourhood of offshore pipelines, mono-pile structures, and multi-cylinder structures. Prior to applying the proposed WSSI models to practical engineering cases, several validations, mainly including wave and soil validations, were conducted. Excellent agreements between numerical and experimental results indicate the capacity of proposed WSSI models to simulate nonlinear wave-induced seabed response around offshore structures. Hereafter, the verified WSSI models are adopted to explore the mechanism of storm wave-induced soil response near offshore structures. The study of the offshore pipeline partially or fully buried in the seabed has shown that the leewake vortex can be sufficiently avoided with enough embedment, which also leads to lower possibility of the onset of scour in adjacent area of pipeline and the reduction of possible momentary liquefaction depth under pipeline bottom. Nonlinear wave-induced seabed response around a mono-pile structure, was investigated using the 3-D WSSI model developed in OpenFOAM, which allows to run numerical WSSI simulations in parallel. It was shown that, for waves propagating in a given longitudinal direction, the liquefaction occurs with greater depth at the lateral sides of mono-pile structure than at the front and back sides of mono-pile structure. Increasing penetration depth of the mono-pile structure slightly reduces the adjacent liquefaction depth. By adopting the same 3-D WSSI model, the numerical investigation of wave-induced soil response in the proximity of a multi-cylinder structure has been conducted. As found in the analysis by using same wave parameters in the case of a mono-pile structure, the nonlinear interaction between waves and multi-cylinder structure may significantly alter the distribution of liquefaction depth around each cylinder, compared to that for a single cylinder. Moreover, considering the effect of incident wave angles, such as 0° and 45° wave headings, it can be noted that the downstream cylinders are better protected from liquefaction threat due to the presence of upstream cylinders.
Supervisor: Not available Sponsor: Energy Technology Partnershp ; Wood Group Kenny ; University of Aberdeen
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Offshore structures ; Ocean waves ; Ocean bottom ; Engineering models