The Measure Of Intermittency And Groupness For Wind Wave Breaking

Intermittency and groupness are the two typical characters for breaking of windwaves. Knowledge on intermittency and groupness of wave breaking is so far limitedto a few summary statistics. Based on a series of experiment data such characters areinvestigated, while we also study the property for the clustering point process modelof wave breaking.This thesis contains three parts: the first is to discuss the measure ofintermittency and groupness; the second is to discuss the dependence oncharacteristics of wind and wave. The major objects which are investigated are themeasure of breaking frequency and the measure of breaking groupness; the third is tofind the effective indicator to reflect the groupness of wave breaking and try toestablish the spatial clustering process model for wind wave breaking.The results from a series hypothesis tests suggest that:1) intermittency of windwave breaking can be clearly described by the probability distribution of timeintervals between breaking groups. Because of breaking waves within a wave groupwere taken as a single breaking event,according to recent studies, interval betweensuccessive wave groups with breaker is the focus of this paper and the groupness ofwave breaking can be mainly expressed by averaged number of breaking waves ingroup;2)The result of A2, we also found these intervals indicate that they all followgamma distribution, estimated α and β correlated with characteristics of wind wavefield, such as significant wave height Hs, significant wave steepness ε and wave age βa,while β has much variation than α. The average breaking-group-interval is αβ, whichis the mean of gamma distribution, and mainly depends on β, averagebreaking-group-interval decreases with u*and ε, until the wind speed or steepness islarge enough, while averaged number of breaking waves in group is opposite3)breaking rate bR, breaking probability bTare highly correlated for significant wavesteepness ε, group breaking rate bRgand group breaking probability bTg, averagednumber of breaking waves in group E(n) are most dependence with wave height Hs, itseems to be a more reasonable and sensitive measure for breaking wave field thantraditional breaking probability defined in terms of single wave.