Mechanics of extreme water waves

Abstract

The design and construction of a versatile new wave flume is described along with associated apparatus and experimental methods. In particular, the practices developed for the use of Particle Image Velocimetry (PIV) for the measurement of the internal kinematics of waves are detailed. Two studies are then described, both of which make use of the PIV technique. In the first, a deep-water long-crested breaking wave is generated in a time-stepping numerical model, then replicated in the wave flume. Measurements of the internal kinematics are made throughout the breaking process, including measurements into the plunging spout. After a small shift of the numerical data to match the surface profiles, the predicted and measured kinematics are shown to agree within about 2%. In the second study, steep steady waves are combined with sheared currents. The resulting kinematics are found to be reasonably predicted in the crest region by adding the results of irrotational computations to the stretched current profile. However, calculation of the vorticity of the measured flow fields indicates that the conditions were not steady, and that the shear of the current was reducing with time.