ACOUSTICAL EMISSIONS FROM BUBBLE CLOUDS

Bubble clouds are believed to be responsible for producing acoustical frequencies much lower than the resonant frequencies of the inherent b ubbles. Earlier models for determining the resonant frequencies of a c loud were based on a uniform void fraction throughout the cloud. In ge neral, the void fraction in a bubble cloud may not be uniform, especia lly in oceanic bubble clouds - referred to as plumes. A new model is p roposed that accounts for a variation in the void fraction as a functi on of position in the cloud. In this work, the cloud is modelled as a cylindrical resonant cavity with a void fraction that decreases with r adius. Experimental results show good agreement with theory. This rese arch provides further evidence that the source of these lower frequenc ies is due to the geometry and void fraction properties of the cloud.