Abstract
A series of laboratory experiments were conducted in a wave-current flume to investigate the scour evolution and scour morphology around tripod in combined waves and current. The tripod model was made using the 3D printing technology, and it was installed in seabed with three installation angles α = 0°, 90°and 180° respectively. In the present study, the scour evolution and scour characteristic were first analyzed. Then, the equilibrium scour depth Seq was investigated. Furthermore, a parametric study was carried out to study the effects of Froude number Fr and Euler number Eu on equilibrium scour depth Seq respectively. Finally, the effects of tripod’s structural elements on Seq were discussed. The results indicate that the maximum scour hole appeared underneath the main column for installation angle α = 0°, 90° and 180°. The Seq for α = 90° was greater than the case of α = 0° and α = 180°, implying the tripod suffered from more severe scour for α = 90°. When KC was fixed, the dimensionless time scale T* for α = 90° was slightly larger than the case of α = 0° and α = 180° and the T* was linearly correlated with Ucw in the range of 0.347 < Ucw < 0.739. The higher Fr and Eu both resulted in the greater scour depth for tripod in combined waves and current. The logarithmic formula can depict the general trend of Seq and Fr (Eu) for tripod in combined waves and current.
Highlights
As a kind of clean and renewable energy, offshore wind energy developed rapidly in recent years
Welzel et al [28,29] carried out a series of wave flume tests to study the scour evolution around jacket foundation, the results implying the streamline contraction and flow acceleration adjacent to the structural elements, resulting in the shear stresses on the seabed amplified and the greater scour depth
A parametric study was carried out to study the effects of Froude number Fr and Euler number Eu on equilibrium scour depth Seq respectively
Summary
As a kind of clean and renewable energy, offshore wind energy developed rapidly in recent years. For the foundation with complex shapes, such as tripod and jacket, the scour process was more complicated than the case of monopile due to the blockage effects induced by structural elements [27–29], so a unique scour morphology around foundation with complex shapes would be expected compared with a single pile. Welzel et al [28,29] carried out a series of wave flume tests to study the scour evolution around jacket foundation, the results implying the streamline contraction and flow acceleration adjacent to the structural elements, resulting in the shear stresses on the seabed amplified and the greater scour depth. Such types of complex subsea structures often present numerous challenging design aspects [33,34], for example, the scour design for tripod usually refers to the criterion for a single pile, leading to an underestimated scour depth This can lead to safety risks for offshore wind farms. The effects of the tripod’s structural elements on Seq were discussed
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