NUMERICAL AND EXPERIMENTAL INVESTIGATION ON THE WAVE-WAVE INTERACTION IN BREAKING AND NON-BREAKING FOCUSING WAVES

摘要

The modelling of large individual waves for the computation of loads on ships and offshore structures inudextreme weather conditions is still a challenging problem. Since the early 50s the predictions of loads onudfixed offshore structures and motions of compliant or sailing structures due to surface waves areudcommonly made by computations on the basis of the statistical/spectral description of the sea elevationudand of a linearized response model. Quadratic Transfer Functions or fully non-linear methods are usedudonly in specific cases. The linear approach is recognized to work reasonably well for the so-calledudoperational conditions, assuming that hydrodynamic and dynamic nonlinear effects can be neglected. Onudthe other hand, it is also recognized that the modelling of large amplitude motions and the modelling ofudwaves in the so-called survival conditions, i.e. extreme wave conditions, cannot recast a linear approach.udIn these conditions the wave-wave interaction plays a fundamental role (energy transfer, down-shift, etc) inudthe actual deterministic or spectral representation of the wave/flow field and thus in the related loads onudthe structure.udIn the present paper the nonlinear aspects related to the behavior of steep focusing breaking and non-udbreaking waves are analyzed by means of numerical simulations and new experiments. The experimentsudare carried out at the wave flume of the Laboratory of Maritime Engineering (LABIMA) of the Dept. of Civiludand Environmental Engineering of the University of Florence. The computations are carried out atudHydrodynamic and MetOcean Laboratory (HyMOLab) of the Dept. of Engineering and Architecture of theudUniversity of Trieste. The paper focuses the attention on the comparison between the results obtained withuda state-of-art viscous flow simulation and laboratory experiments, with particular emphasis on the spectraludenergy exchange between component waves of a non-breaking and breaking focusing wave train. Thisudstudy is carried out as part of the research project “OpenViewSHIP Development of an integratedudcomputational ecosystem for the hydrodynamic design of the hull-propeller system”, co-financed by FriuliudVenezia Giulia Region in the field of industrial application of open-source CFD and High PerformanceudComputing.