Envelope Interaction In Wave Group And Wave Group Properties Study

Research on ocean wave group is important for ocean wave theory and oceanengineering.Research on ocean wave nonlinearity is an important realm of oceanwave study.The nonlinear wave-wave interactions are studied intensively.Interactionbetween wave components causes asymmetry of wave surface.However,there is littleresearch on whether the wave groups interact with each other and the asymmetry ofwave group envelope.Most of researchers study wave group based on the envelopestatistical theory.The envelope is assumed to be symmetrical in those documents.However,the possibility of interaction between wave groups and the asymmetry ofwave group envelope are not studied.The wind wave field should be treated as superposition of many kinds of simple wavegroups.Results of wind wave experiments show that wind wave field is not linearsuperposition of simple wave groups,which means that there is nonlinear interactionbetween different simple wave groups.Results of many theoretical researches showthat the evolvement of wave group envelope is controlled by nonlinear Schr(o|¨)dingerequation.This means that the interaction between wave group envelopes can bestudied in the framework of nonlinear Schr(o|¨)dinger equation.Nonlinear interactionbetween different simple wave groups is studied based on nonlinear Schr(o|¨)dingerequation theory in this work.It shows that the interaction between different simplewave groups causes the wave group envelope become asymmetric.The Asymmetrycaused by the interaction between envelopes induces that the highest individual wavehappens one wave length in advance.The theoretical results also show that the degreeof envelope asymmetry increases as the structure of spectrum broadening,andincreases as the average steepness increasing.The experimental results show that wind wave group envelope is asymmetric.Thedegree of the wind wave group envelope asymmetry corresponds to the theoreticalresult.The asymmetry of wind wave group envelope causes the highest individualwave happening one wave length in advance.The experimental results also show thatthe degree of envelope asymmetry increases as the structure of spectrum broadening,and increases as the average steepness increasing.The theoretical results accord withthe experimental results.Distributions of individual wave steepness in wave group areanalyzed.It is found that individual wave with smaller sequence number is steeperthan that with bigger sequence number.This phenomena correlate with the asymmetryof wave group envelope.It is found that individual waves in the front of wave groupsare of larger breaking probability.