The computation of second-order wave loads
Academic Article
Overview
Overview
abstract
The second-order wave loads which act on an offshore structure include mean, difference-frequency, sum-frequency, and second-harmonic components. These are of special importance to vessels with low- or high-frequency resonant features outside the spectral range of wave encounter. Special numerical techniques are required to evaluate the second-order loads. The most difficult component, associated with the boundary condition on the free surface, requires the evaluation of slowly-convergent oscillatory integrals over this surface. Numerical methods are described for evaluating the second-order loads, based on extensions of the first-order panel method and applicable to three-dimensional structures of arbitrary geometric form. Illustrative results are presented for the second-harmonic and sum-frequency diffraction loads on the ISSC TLP, in monochromatic and bi-chromatic waves. Emphasis is given to the solution of the second-order free-surface condition, which is the dominant source of sum-frequency vertical loads. (A)
