Hydrodynamic aspects of ship collisions with tension leg platforms

Abstract

Collisions of tension leg platforms with ships are numerically simulated and their consequences predicted. A non-linear mathematical model is formulated; it accounts for two-dimensional kinematics of the colliding bodies, the local forcedeformation characteristics within the impact zone of both structures as well as the restoring forces induced by the pre-tensioned legs. Particular emphasis is given to the rigorous modelling of the hydrodynamic interaction between the floating vessels and the fluid in their vicinity. This is achieved through unit impulse response functions that provide the damping forces as convolution integrals involving the histories of fluid motion and inertia terms with constant coefficients giving rise to added masses. The derived integro-differential equations are numerically solved in the time domain. Various collision scenarios are analysed and results are obtained for collision and hydrodynamic forces as well as the extent of local damage. The hydrodynamic effect is linked to the duration of impact. Thus, the problem is addressed in a more rational and mathematically rigorous manner than that of the classical impact theory. © 2013 WIT Press.