Experimental inquires into collective sea state modes in deep water surface gravity waves

Abstract

an experiment designed to find collective sea state modes in deep water surface gravity waves was performed. The experiment was conducted in a large water tank with fans to create wind a driven background sea state. This background sea state may be more precisely referred to as a condition of wave turbulence. The background sea state was perturbed with an additional burst of waves created at one end of the tank by a computer controlled mechanical paddle. Different wind speeds and input burst waveforms were used. The wave height was measured with a four wire probe, with integrated circuit implementation. Data acquisition, manipulation, and averaging were automated. The probable collective mode can be seen in spectral density versus time images as a nondispersive decrease in background spectral density. It was estimated that this decrease is spectral density propagated independently of the input wave burst by examining its arrival time relative to burst energy arrival time for difficult probe to paddle distances. More importantly, it was determined that the propagation speed was a function of the background spectral peak frequency. Additionally, input burst energy at frequencies above the background spectral peak was not observed to propagate.