Numerical simulation study of vortex-induced motion with coupled multi-degrees of freedom on Spar platform

In order to study the vortex-induced motion characteristics with coupled multi-degrees of freedom of Spar platforms under a uniform flow, a numerical model about the vortex-induced motion of a Spar plat⁃ form considering fluid-structure interactions was established based on STAR-CCM+, and the coupling ef⁃ fects of five-degrees of freedom (surge, sway, heave, pitch and roll) were investigated. The results show that the vortex-induced resonance can be observed obviously at three degrees of freedom (sway, heave and roll), and the velocity interval of vortex-induced resonance is the same at the two degrees of freedom (heave and roll). Meanwhile, the coupling effects between sway and roll are obvious. In the case of sway resonance, the relationship of the dominant frequency between sway and roll is 1:1, and in the case of roll resonance, the sec⁃ ondary peak frequency of sway is the same as the dominant frequency of roll. Moreover, there are complex nonlinear coupling relationships among the three degrees of freedom (surge, heave and pitch), not only the dominant frequency of surge and heave always exists in the pitch spectrum, but also the coupling effects be⁃ tween pitch and surge, pitch and heave are various in the different ranges of reduced velocity. © 2024 China Ship Scientific Research Center. All rights reserved.