Second order approximation of wave-structure couplings

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Second order approximation of wave-structure couplings

Huang, E.T. / Hwang, Y.L.

This study explores the significance of second order wave forces on a box-shaped pontoon in shallow weater and tests the feasibility of the perturbation approach for free surface problems involving shallow draft structures. A simulation model developed for these purposes is described that solves the reduced linear boundary value problems with a versatile, finite element procedure. This procedure, which achieves a fair compromise between computation costs and physical details, is particularly suitable for practical applications. A simple hydraulic model test was conducted to observe the wave forces imposed on a rectangle box by a steep wave in shallow water. The second order contribution to the total wave force was found to increase with the Ursell number, HL²/h³), in a manner resembling that of the second order waves to the exciting waves. The test results favorably support the perturbation approach for the analysis of nonlinear wave forces on shallow draft pontoons. However, more sophisticated model tests are required for a full is justification. Both theoretical and experimental results show profound second order forces that are sufficient to impact the design of pontoon facilities.