Statistical properties of mechanically generated surface gravity waves: a laboratory experiment in a three-dimensional wave basin

TLDR

The experiment investigates how directional energy distribution affects the statistical properties of surface gravity waves. Different degrees of directionality were examined—from long‑crested waves to ±30° spread at the spectral peak—with a focus on the tails of the surface elevation, wave height, and crest distributions, and the results were compared to a simplified second‑order theory model. The findings indicate that second‑order theory underestimates the probability of large waves for long‑crested, steep, narrow‑banded conditions, but as directional spreading increases, this discrepancy diminishes and the surface elevation statistics approach Gaussian behavior.

Abstract

A wave basin experiment has been performed in the MARINTEK laboratories, in one of the largest existing three-dimensional wave tanks in the world. The aim of the experiment is to investigate the effects of directional energy distribution on the statistical properties of surface gravity waves. Different degrees of directionality have been considered, starting from long-crested waves up to directional distributions with a spread of ±30° at the spectral peak. Particular attention is given to the tails of the distribution function of the surface elevation, wave heights and wave crests. Comparison with a simplified model based on second-order theory is reported. The results show that for long-crested, steep and narrow-banded waves, the second-order theory underestimates the probability of occurrence of large waves. As directional effects are included, the departure from second-order theory becomes less accentuated and the surface elevation is characterized by weak deviations from Gaussian statistics.