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Publications
Rajendran, S. and Guedes Soares, C. (2018), “Short term statistics of hydroelastic loads of a containership in head and oblique seas”, Proceedings of the ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2018), 17-22 June, Madrid, Spain
As the ships are getting longer and larger in dimension, hydroelasticity has become an important topic in the area of ship design. The term hydroelasticity of ships implies that the structural deformation changes the radiation field and thus the structural and the hydrodynamic forces are fully coupled. This generally occurs when the hull girder natural frequency lies in the vicinity of the harmonics of the wave loads. Large increase in demand for longer and larger containerships with capacities varying between 8000-14000 TEU and length up to 400m has reemphasized the importance of hydroelasticity in ship design. Due to their open hull structure and the long hulls, the natural frequency (Eigen frequencies) of the hull girder falls within the vicinity of the wave induced loads. Therefore, the containerships are highly susceptible to springing and whipping, among which the former leads to fatigue failure, and the latter is important for the structural design as it imparts huge impact load on the structure and can also be a cause of fatigue failure. In this paper, a 2D body nonlinear time domain method developed by the authors will be used to calculate the symmetric response of an ultra large containership ship in extreme sea conditions. The hydrostatic and the Froude-Krylov forces are calculated for the exact wetted surface area under the incident wave profile. The radiation forces are represented by means of convolution integrals based on |Cummins formulation. The memory function are calculated from the frequency dependent coefficients based on the analogy between the frequency domain and time domain formulation for the linear problem. The hydrodynamic coefficients are also calculated for the exact wetted surface area under the incident wave profile. The numerical method enables a real time calculation of the long time series simulations, which in turn can be used for generation of short term distribution of nonlinear loads. The numerical results are compared with the experimental results that were measured in a wave tank.
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