STOCHASTIC CHARACTERISTICS OF WAVE KINEMATICS IN LABORATORY-SCALE RANDOM WAVES

This paper presents the results of analysis of wave kinematics data of Skjelbreia et al. taken in a wave flume using Laser Doppler Velocimet ry. This data set is unique with respect to accuracy and amount of dat a in the vicinity of the mean water level. The present publication of the statistical and spectral characteristics of these data sheds furth er insight into wave kinematics mechanism in the free surface zone whe re measurement points an not continuously submerged and when the so ca lled ''emergence effect'' should be taken into account. Stochastic cha racteristics estimated from measurements are compared with known theor etical predictions applying the not commonly used approach presented b y Tung. Furthermore, the theoretical spectral density of particle velo cities, modified by emergence effect, obtained by taking the Fourier t ransform of the covariance function as derived by Pajouhi and Tung, is compared with measured values. Such a comparison has previously been made by Anastasiou et al. for a data set with limited amount of data a bove the free surface elevation. Anastasiou et al. have used an approx imate formula for the modified covariance function. In this paper, how ever, the exact modified covariance function is for the first time use d for statistical analysis and comparison with measurements of wave ki nematics in a wave flume.