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 Velocimetry. This data set is unique with respect to accuracy and amount of data in the vicinity of the mean water level. The present publication of the statistical and spectral characteristics of these data sheds further insight into wave kinematics mechanism in the free surface zone where measurement points an not continuously submerged and when the so called ''emergence effect'' should be taken into account. Stochastic characteristics estimated from measurements are compared with known theoretical predictions applying the not commonly used approach presented by Tung. Furthermore, the theoretical spectral density of particle velocities, modified by emergence effect, obtained by taking the Fourier transform 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 above the free surface elevation. Anastasiou et al. have used an approximate formula for the modified covariance function. In this paper, however, the exact modified covariance function is for the first time used for statistical analysis and comparison with measurements of wave kinematics in a wave flume.