The reflection of nonlinear irregular surface water waves

This paper concerns the reflection of irregular surface water waves from an impermeable vertical wall and investigates the similarities between this case and the direct, head-on collision of two identical wave groups travelling in opposite directions. A new set of experimental measurements is presented and compared with fully nonlinear numerical predictions based upon a multiple-flux boundary element method (BEM). Comparisons concern both the spatial and the temporal water surface elevations in the vicinity of the focused wave event; the latter occurring at the location of the wall. Linear and second-order irregular wave theories, commonly adopted as the basis for design solutions, are shown to significantly under-predict both the wave steepness and the maximum crest elevation in the vicinity of the wall. In contrast, the fully nonlinear numerical predictions are shown to be in very good agreement with the experimental measurements; the present results having been achieved without the need for smoothing, filtering or regridding.