Wind-Wave Energy Flux Measurements using Particle Image Velocimetry

Abstract

<p>Small-scale processes govern the transfer of energy and momentum at the coupled atmospheric and oceanic wave boundary layers. The physical wind energy input mechanisms by wave growth remain poorly understood (critical layer theory vs sheltering mechanism).</p><p>We conducted laboratory velocity measurements within the first millimeters to centimeters above and below surface waves. A high resolution 2D Particle Image Velocimetry (PIV) system was installed in a wind-wave tunnel at a fetch of approximately 10 m. In addition, wave field properties were captured by Laser-Induced Fluorescence (LIF). Experiments were run with wind waves and wind over mechanical swell. During the measurements, 10-m wind speeds of 5 to 10 m/s were observed, with peak wave ages (<em>c<sub>p</sub>/u<sub>*</sub></em>) ranging from 1 to 7.</p><p>We will focus on the air phase and describe the modulations of the airflow structure. Furthermore, we will discuss the influence of peak wind-wave conditions (e.g., wave age, slope) on the dynamical role of the critical layer.</p>