Multi-body-based 2D hydro-elasticity simulations in time domain for moored floating structure

초록

This study presents the two-dimensional (2D) hydro-elastic characteristics of a large, moored box barge. The multi-body-based Discrete-Module-Beam (DMB) method was extended to incorporate both longitudinal and lateral hydro-elastic behaviors in time domain. The present model, referred to as the 2D DMB model, includes 3D multi-body hydrodynamics based on the Cummins equation and structural dynamics using the Finite Element (FE) Based Euler-Bernoulli beam equation. Mooring dynamics were modeled by FE-based rod theory. The method was validated by comparing the vertical elastic displacements of freely floating box barge in waves between the present numerical simulation and the previous experiment. Subsequently, the importance of the developed 2D DMB model was discussed by comparing the results with 1D DMB and rigid-body models. Moreover, effects under second-order wave loads were evaluated. The importance of mooring dynamics was further assessed by comparing the results with the cases without mooring lines or with simple linear springs as a replacement for mooring lines. The analysis focused on presenting and systematically interpreting mode shapes, vertical displacements, and mooring tensions. The result demonstrates the importance of the 2D DMB method for increased barge width and in oblique seas. The second-order wave loads play a minimal role in dynamic behaviors at the representative regular waves. The taut mooring lines play important roles in nonlinear interaction by limiting positive vertical displacements and changing overall motion trends.

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