Abstract
In the present study, as a novel and alternative form of foundation for offshore wind turbines, the air-floating characteristics of a large-diameter multi-bucket foundation (LDMBF) in still water and regular waves are investigated. Following the theory of single degree of freedom (DOF)-damped vibration, the equations of oscillating motion for LDMBF are established. The spring or restoring coefficients in heaving, rolling and pitching motion are modified by a dimensionless parameter ϑ related to air compressibility in every bucket with the ideal air state equation. Combined with the 1/25 scale physical model tests and the numerically simulated prototype models by MOSES, the natural periods, added mass coefficients and damping characteristics of the LDMBF in free oscillations and the response amplitude operator (RAO) have been investigated. The results shown that the added mass coefficients between 1.2 and 1.6 is equal to or larger than the recommended values for ship dynamics. The coefficient 1.2 can be taken as the lower limit 1.2 for a large draft and 1.6 can be taken as the upper limit 1.6 for a small draft. The resonant period and maximum amplitudes for heaving and pitching motions decrease with increasing draft. The amplitudes of heaving and pitching movements decrease to a limited extent with decreasing water depth.
Highlights
Under the dual pressures of a deteriorating ecological environment and depleting fossil energy, investigations on the utilization of renewable energy have increasingly become a worldwide focus
The results showed that the hydrodynamic responses of the large floater with air cushion depended on the wave conditions and on the mass of the water column, the height of the air cushion, and the air-pressure distribution [16]
The results showed that a smaller draft and a larger air cushion contribute to a safe transportation process [8]
Summary
Under the dual pressures of a deteriorating ecological environment and depleting fossil energy, investigations on the utilization of renewable energy have increasingly become a worldwide focus. The application of wind-power generation shows that it is one of the most mature, largest-scale renewable energy technologies with the prospect of commercial development [1,2]. With the advancement of technology and the decline in costs, the size of the global offshore wind power market has expanded rapidly. The bucket foundation is one of the foundation types used in recent years for offshore wind-power development. The mono-bucket foundation (e.g., developed by the Universal Foundation) was applied to the Frederikshavn wind farm in Denmark in
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