Experimental study of local scour around tripod foundation in combined collinear waves-current conditions

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.