Optimum dynamic response of a floating vessel restrained by cables: a parametric analysis

The dynamics of a floating vessel restrained by cables is analyzed and an optimum parametric analysis of the mooring lines is developed. A frequency domain approach to the linearized problem is adopted. Namely the hydrodynamic boundary value problem is recast in integral form by using the proper Green function and the relevant integral equations are numerically solved. A variational formulation for the cable dynamics is then proposed and its frequency response matrix is obtained in a closed analytical form by a Rayleigh-Ritz approach. The procedure is applied in the frame of an optimization technique and the sensitivity of the moored vessel response to some mooring line design parameters is investigated. Two basic advantages of the proposed procedure are enlightened. First the frequency approach avoids heavy numerical computations in the time domain. Moreover the impedance matrices formulation allows to update only the cable dynamic response during the iterative optimization. Numerical simulations are presented to show the effectiveness of the method.