Modeling and Numerical Simulation of Tethered Buoy Dynamics

MOX 66

Modeling and Numerical Simulation of Tethered Buoy Dynamics

Friday 29th July 2005

Montano, Antonio; Restelli, Marco; Sacco, Riccardo

In this article we deal with the numerical simulation of the dynamics of a tethered buoy, which is a mechanical system for marine applications consisting of a rigid floating bonding (buoy) connected by an elastic cable to the bottom of the fluid environment. A novel mixed finite element formulation is proposed for the spatial numerical approximation of the equations governing the dynamics of the elastic cable. This is done to allow a robust modeling of the cable, event in the limit of an infinite value of the Young modulus, in a way that is similar to mixed formulations for incompressible fluid-mechanics. The dynamics of the floating bodyis described by the classical Euler equations of motion, written using quaternion variables to end up with a numerically robust algorithm in presence of large rotations. For the time discretization of the resulting coupled system of nonlinear differential equations, the Backward Euler implicit method is adopted due to the stability requirements of the problem at hand, while a damped Newton method is used for linearization. Finally, the accuracy and robustness of the proposed numerical procedure are validated in the simulation of the tethered buoy system under various static and dynamic working conditions.