On Statistical Properties of Artificial Irregular Water Wave (Part2) : On Wave Slope

Abstract

Generally the wave slope is important characteristic especially in connection with angular motions of floating body. But, in spite of this fact, there are very few reports discussed the wave slope in irregular water wave. The previous report (KSRNo.195) has mainly investigated on statistical characteristic of the wave elevation in artificial irregular water wave. Therefore this report newly treats characteristic of the wave slope in irregular deep water wave. By recently developed instrumentation, wave elevation and wave slope timehistory were simultaneously measured at the fixed point. We calculated directly statistics of these amplitudes and periods, and estimated the power spectra of wave elevation and wave slope too. The relation between the direct statistics of measured wave slope timehistory and the estimated values from wave slope spectra was exactly investigated as well as the case of wave elevation. It was shown from these analysis that linear relations between wave elevation and wave slope exist in most case of artificial irregular deep water waves, but drastic nonlinear phenomena appear in wave slope of high and steep irregular water waves, and there is a upper limit value of the maximum wave slope because of breaking of individual waves, and that value is approximately equal to 0.6. Moreover, the statistical characteristics of wave length and wave steepness were clarified. Thus, we showed the various statistical informations on the wave slope of irregular waves were found from the measured irregular wave slope timehistories. Then we think that these results can be applied in the actual deep ocan wave.