Nonlinear loading of a two-dimensional heaving box

• The excitation, radiation and floating problem of a heaving box are considered.
• Comparisons to a fully nonlinear potential flow method are provided.
• Key sources of nonlinear forcing are identified and explained.
• Significant harmonic motion content is observed in more than one wave regime.
• The importance of both nonlinear forcing and dynamic response is considered.

A numerical investigation is presented addressing the nonlinear heave response of a rectangular box. The work specifically concerns the importance of the relative body dimensions, expressed through the product of the half-beam b and the wavenumber k  . When subjected to moderately steep incident waves, the second-harmonic content of the heave motion is found to be as large as 25% of the first-harmonic content. In considering the extent of this second-harmonic motion, three regimes may be defined: (i) the long wave regime, where kb≤0.4kb≤0.4, (ii) the intermediate regime, where 0.4