The paper proposes a numerical method for analyzing nonlinear wave loads using a hydroelastic model. The numerical analysis method utilizes a 3-D Green function method and a 2-D momentum model, which are coupled in the time domain. The computational results were compared with those of a model test of a 10000-TEU containership. The different components (low frequency wave component, high frequency whipping component and combined total component) of experimentally and numerically determined sectional vertical bending moment (V.B.M) to regular waves were compared. Furthermore, discussions are made on how much the whipping component contributes to the total V.B.M, which are observed and calculated in regular waves, and how to choose the design wave loads and combine different components of vertical bending moment.
With the demand of the world transportation increases, it is a must for the marine corporation to make the ship in large scale. To the ultra-large containership with high speed which may sail under severe conditions in different sea states, when the level of sea state increasing, the severe relative motion between ship and wave occurs may result in slamming loading and whipping response in ship hull structures. This brings new requirements to fatigue strength and ultimate strength of ultra-large containership, and it has been a research hotspot for researchers and Classification Societies around the world that how to use direct calculation method to modify the rules.(Drummen, Wu et al. 2009) Recent studies have revealed that whipping significantly affects the fatigue strength and ultimate strength(Drummen, Storhaug et al. 2008, Hirdaris and Temarel 2009, Storhaug, Choi et al. 2010, Storhaug, Derbanne et al. 2011).Numerical simulation of whipping can be found in many recent papers (Hirdaris and Temarel 2009, Tuitman 2010, Drummen and Holtmann 2014, Kim and Kim 2014).
Till now, theoretical calculation combined with model test is treated as a most effective approach, therefore reliable model test data is needed to verify and validate the accuracy and applicability of the computational programs, thus it's possible to make use of the programs at the preliminary stage of ship design in order to decrease the cost. Recently, model tests of linear and nonlinear wave loads were conducted at the towing tank of Harbin Engineering University. The model test system for the measurement of linear and nonlinear wave loads which is composed of a backbone and segmented container ship model in which natural frequency of vertical bending is matched using a beam with rectangular-shaped variable cross-section, has already been built up and applied to a series of large ship models especially. A series of model tests have been carried out for selected cases in regular and irregular waves.