On the Low-Frequency Hydrodynamic Damping Forces Acting on Offshore Moored Vessels
Moored floating structures for drilling, production-storage-offloading or other purposes are being installed in ever increasing water depths and in areas where the environmental conditions are also more severe. Such structures, moored permanently in high seas, have to survive safely the most severe weather conditions. Therefore it is of importance to understand the mechanisms which govern the motions and the mooring forces of these facilities.In deep water the mooring systems inevitably have soft elasticity characteristics. With the increase in the elasticity of the mooring, the low frequency horizontal motions induced by low frequency second order wave drift forces also become larger. The low frequency resonant motion components completely dominate the horizontal motions and, consequently, also the mooring forces. In order to predict the amplitudes of the low frequency resonant motions the magnitude of the second order wave drift forces and the values of the low frequency hydrodynamic damping must be known.