Influence of irregular waves on the dynamic response of a vertical transport system for deep sea mining

摘要

The vertical transport system (VTS) is the main part of the total integrated system for deep sea mining, which attracts increasing attention owing to the shortage of mineral resources. The influences of irregular waves due to wave-induced hydrodynamic forces and wave-induced vessel motions on the VTS dynamic responses are estimated based on the lumped-mass method. Results show that the wave-induced hydrodynamic forces mainly act on the equilibrium position of the VTS, whereas the wave-induced vessel motions are the determining factor in the VTS dynamic responses. Waves with the specific spectrum peak period would induce parametric instability in the VTS. The most adverse heading for the VTS is found to be 90°. The dynamic responses of the VTS will increase with wave heights. However, the buffer-miner slant range is found to be insensitive to wave conditions. Heave motions are the most dominant factor influencing the effective tension of the rigid pipe. The effective tension on the rigid pipe directly affect the load response of the hose. Particularly, the bending moment on the rigid pipe presents non-Gaussian characteristics under extreme environments. Therefore, the coupling effect of the vessel motions under irregular waves should be considered to study the complete VTS dynamic responses.