Statistical Distribution of Wave Orbital Velocity in Finite Water Depth

Abstract

A comprehensive field study was undertaken to determine the statistical distribution of wave orbital velocity in finite water depth. Two ocean ADV current meters were mounted on two separate stainless steel tripods to measure horizontal wave orbital velocity components ) , ( v u and wave pressure ξ at a sampling rate of 2Hz for 17.07min every hour at 0.5m above the seabed in two coastal water depths of 12m and 24m. The zero-crossing method was then applied to analyse the collected field data to obtain wave orbital velocity maxima U of individual waves. It is found that the statistical distributions of ũ , ṽ and ξ are identical and obey Gaussian distribution as commonly assumed, and that the statistical distribution of U deviates from the Rayleigh distribution as U becomes larger. A two-parameter Weibull distribution is also proposed to compute the average orbital velocity U p of the first n largest orbital velocity maxima more accurately than the Rayleigh distribution.