Experimental investigation on mean velocity and turbulence in irregular waves over a sloping bottom

An irregular wave field experiment over a sloping sand bottom, from deep waters up to the surf zone, was performed in a laboratory channel, with the aim to examine the turbulent processes. The instantaneous 3D velocities and elevation measurements were collected simultaneously and at the same locations, along the central longitudinal section of the channel, by means of a 3D ADV and an ultrasonic gauge, respectively. The ensemble averaging technique was used to decompose the velocity into mean, orbital and turbulent components. In fact the key aspect of estimating turbulence in irregular waves is to isolate the turbulent motion from the wave-induced motion, which usually change in an irregular manner. Fields of wave velocity, turbulent kinetic energy (TKE) and TKE transport below the trough, were investigated. Relevant results were deduced on the wave field and on turbulent transport.