An evaluation of directional analysis techniques for multidirectional, partially reflected waves .1. numerical investigations

Recent studies of advanced directional analysis techniques have mainly cent red on incident wave fields. In the study of coastal structures, however, p artially reflective wave fields are commonly present. In the near structure field, phase locked methods can be successfully applied. In the far field, non-phased locked methods are more appropriate. In this paper, the accurac y of two non-phased locked methods of directional analysis, the maximum lik elihood method (MLM) and the Bayesian directional method (BDM) have been qu antitatively evaluated using numerical simulations for the case of multidir ectional waves with partial reflections. It is shown that the results are i nfluenced by the ratio of distance from the reflector (L) to the length of the time series (S) used in the spectral analysis. Both methods are found t o be capable of determining the incident and reflective wave fields when US > 0.5. The BBM provides, in most cases, more accurate estimates of inciden t significant wave height, average reflection coefficients and directional spreading.