Abstract
Simultaneous measurements of the surface gravity wave field, void fraction entrained during breaking, and the generated acoustic spectra were made in a sand beached wave tank at the Center for Applied Coastal Research at the University of Delaware during April 2002. The tank has the dimensions of 30 m (l)×2 m (w)×1.5 m (d) and a 0.2-mm sand beach. Four hydrophones were distributed along the sand beach beneath the region of active breaking. Wave gauges measured surface gravity wave properties along the beach cross-shore. Conductivity and temperature probes allowed for the measurement of the void fraction of the entrained bubble cloud. A video camera captured the evolution of the entrained bubble cloud through the tank’s PlexiglasTM side panel. The paper presents generated acoustic power levels as a function of surface wave amplitude and period. Initial results in obtaining the relationships between void fractions of the entrained bubble clouds and the spectral components of the generated acoustic signal will also be discussed. [Work supported by ONR base funding at NRL.]