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• Higher-order springing phenomenon is investigated through experimental and numerical measures, examining harmonics up to 14th order. • A segmented barge model was chosen, with careful observations to capture springing vibrations only. • A direct coupled method between CFD-FEM is developed and used to reproduce the springing phenomenon numerically. • The performance of the numerical model is discussed in comparison with experimental results by dissecting individual harmonics. In this paper, the higher-order springing phenomenon is addressed for a segmented barge ship model through experimental and numerical measures. An efficient in-house two-way coupled numerical solver between Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) is developed and validated against experimental results. The coupling method is based on a domain-separated approach and necessitates the resolution of individual boundary value problems in distinct domains. To ensure convergence within these individual domains, an implicit numerical scheme is employed and further facilitated exchange of variables for coupling. The current approach emphasizes the overall convergence between two solvers, maintaining a strongly coupled setup to comprehensively address fluid-structure interaction phenomena, including added mass and damping effects. A series of tank tests were conducted first to measure the wave-induced sectional loads and motions, during which the springing responses to very high-order harmonics of wave load were observed. By comparing the numerical prediction with the tank test results for rigid body motion and flexible vertical bending moment (VBM), the proposed numerical method demonstrated agreement with experimental results, affirming its validity and robustness. Finally, the springing response up to 14th order harmonics is discussed and investigated. [ABSTRACT FROM AUTHOR]

The paper introduces a simplified coupled computational fluid dynamics-boundary element method-finite element method (CFD-BEM-FEM)-based approach to study the effect green water induced loading on global structural responses such as bending moment and shear force. The proposed numerical scheme is based on a coupled three-step model. Initially, rigid modes of structural motions are calculated adopting a three-dimensional (3D) time domain panel method without incorporating the green water loading. The time histories of the green water impact on the deck are computed using a finite volume-based CFD tool with these precalculated rigid body motions. Finally, the problem of fluid-structure interaction is solved by considering the green water force as an external input. The direct integration scheme (i.e., Newmark-Beta method in the time domain) is employed to solve this structural problem modeled with one-dimensional FEM. To check the robustness and efficacy of the proposed model and to evaluate green water effect on the structure and vice versa, a large container vessel with and without forward speed is investigated. The impact is studied with respect to motion, shear force, and bending moment. The results confirm that the impact of green water and structural flexibility is significant. Therefore, these effects must be considered while designing a container ship. Also, from the results, it appears that the present three-step model is an effective, efficient, and useful practical tool to predict such effects. [ABSTRACT FROM AUTHOR]

An extreme value distribution method for the vertical bending moment (VBM) is developed using a reduced order model (ROM) based on CFD-FEM coupling. A post-Panamax containership is considered to be a subject model and for which experiment was performed in our previous study. In ROM, VBM for all the components, i.e., wave-induced, whipping, and springing components, are calculated separately and superimposed. The vessel motions and wave-induced components are estimated from transfer functions derived from nonlinear strip theory and later corrected using CFD-FEM coupling. The whipping component is evaluated using von Karman's momentum theory with proper adjustment to specific hull parameters and additionally corrected using CFD-FEM coupling. A new semi-empirical springing ROM is developed based on CFD-FEM coupled analysis and experimental results. A numerous number of irregular waves are generated for a severe short-term sea state using random numbers, for which VBM time series is compared between ROM and coupled CFD-FEM analysis. The effect of springing and whipping in calculating the extreme value distribution of VBM is described for different probability levels. The effect of consecutive bow-stern slamming is also discussed. The development of this method will aid to attain real-time shipload prediction without expensive computational costs due to coupled CFD-FEM. • Extreme value distribution of vertical bending moment (VBM) is calculated based on CFD-FEM coupling. • Instead of directly using CFD-FEM coupling, a Reduced Order Model (ROM) is developed to produce the same physical phenomenon. • To incorporate whipping in ROM a simple momentum theory is used. • The springing ROM model has been developed based on the agreement between CFD-FEM and the experiment. • The performance of the current model is discussed in comparison to the experimental results. [ABSTRACT FROM AUTHOR]