On the Covariance of the Velocity Components in a Wave Field

The present paper presents the first experimental results of covariance distribution of horizontal and vertical velocities of a regular wave field. The analysis of the wave-induced currents, shear stresses, sediment transport, etc. depends on the correlation between the velocity components. Particularly, the undertow is driven by the local difference between radiation stress and the set-up pressure gradient which only balance each other in average over the depth. Turbulent shear stresses are required to maintain a steady condition. Some authors propose models on turbulence shear stresses, but measurement results which may confirm their validity are rare. This paper reports of a preliminary study aimed at comparing experimental measurements with model results.