The Characteristic Index Distinguishing Breaking Wave Groups From Non-Breaking Wave Groups

The groupness is a significant feature of wind wave breaking.Recent studies have shown that the analysis of wind wave breaking should base on wave group instead of single waves.Based on a series of wind wave breaking experiments,this paper investigates distinguishing characteristic indexes of breaking wave group which are quite different from those of non-breaking wave groups.Breaking wave groups were determined by multi-breaking criteria and mark signal recorded in situ simultaneously.The statistical distributions of 28 indexes on breaking and non-breaking wave groups was discussed,including indexes of wave groups,geometric indexes of single waves,local breaking criteria indexes,geometric indexes of wave envelope and indexes represent wave group energy structure.The results show that for wave steepness,crest front steepness,instantaneous wave slope,index in kinematic and dynamic breaking criteria,few overlaps can be found in their distributions on breaking and non-breaking wave groups,especially for the last two indexes,which in kinematics and dynamic breaking criterion.They are distinguishing characteristic indexes of breaking wave group.Other indexes can't be used to distinguish breaking and non-breaking wave groups owing to varying degree overlap of their distributions on breaking and non-breaking wave groups.