Proposal of the 3-DOF model as an approach to modelling offshore lifting dynamics

This paper presents the challenges faced in modelling marine operations with a particular focus on lifting in air. Those challenges are looked at from a purely modelling perspective showing various approaches encountered in the literature. Paper further discusses the disadvantages of those models and proposes a 3-DOF solution that allows to observe all of the physical phenomena and their possible relation enabling efficient, in-depth studies of the operations in discussion. The proposed model is presented in detail starting from a computation of excitation, through the numerical approach with a variety of interesting results. An advantage of the presented approach is seen in the analytical modelling what allows for a theoretical, numerical and combined analysis. The model allows for an implementation of a variety of excitation types providing an ability to study responses to regular and irregular wave. A phenomenon of a parametric resonance was discovered what allows for a reliable assessment of dynamic behaviour, emphasising another advantageous feature of the model in comparison to other approaches discussed. Paper is concluded by a validation of the proposed methodology. It is also suggested that the model proposed is a good, computationally viable, easily accessible balance between overly simple and overly complex models.