Measurements of the Orbital Velocities of Sea Waves and their Use in Determining the Directional Spectrum

Abstract

The three components of orbital velocity in sea waves approaching a shore have been measured using an electromagnetic flowmeter. The spectra of these components have been compared with the spectrum of the pressure oscillations recorded at the same time. From these data, the relations between the pressure and velocity components at various heights above the bottom have been investigated and have been compared with those given by first order potential wave theory. The spectra of the wave pressure and two horizontal velocity components have then been combined so as to yield an estimate of the directional spectrum of the waves. The method was found to work satisfactorily but, because of the complicated bottom topography near the site of these experiments (off the Gladstone Dock, Liverpool), the results obtained cannot be related to the properties of the waves in deeper water. Copyright © 1966, Wiley Blackwell. All rights reserved