An experimental study of collective sea state modes of deep water surface gravity waves

Abstract

Experimental tests of the theory of collective sea state modes of deep water surface gravity waves were made in a 20 meter long, 1.1 meter wide wind-wave tank. First, bursts of broadband wave energy were injected into the upwind end of the tank with a paddle. According to wave turbulence theory and previous experiments, it is expected that the collective mode can be seen as a change in the wind generated background spectral density propagating down the tank. The collective mode is expected to give an anomalous phase shift between the wind generated waves and the lowest tank modes. A series of experiments were conducted to measure the phase of the lowest oscillatory modes of the tank at which increases in the magnitude of wind generated waves occurred. Finally, the surface tension of water in the tank was measured in order to better characterize our system. Although our experiments suggest that the collective mode may indeed exist, the results, so far, remain inconclusive.