LINEAR VIBRATION CHARACTERISTICS OF CABLE–BUOY SYSTEMS

A theoretical model for the linear vibration of a cable tensioned by a subsurface buoy is developed. The equilibrium of the cable–buoy system subject to drag is evaluated using an approximate closed-form solution whose range of validity is confirmed through comparison with numerical solutions. The three-dimensional equations of cable–buoy motion are linearized about this equilibrium and then used to assess vibration characteristics. The characteristic equations for the natural frequencies of both in-plane and out-of-plane vibration modes are derived. The in-plane natural frequency spectrum exhibits the curve veering phenomena due to asymmetry of the associated mode shapes. Parameter studies reveal the dependencies of the in-plane and out-of-plane vibration modes on the cable tension, the buoy mass, and the current velocity.