Paul A. Hwang
Res. Div., QUEST Integrated, Inc., 21414 68th Ave. S., Kent, WA 98032
Ron A. Roy
Lawrence A. Crum
Univ. Washington, Seattle, WA 98105
Theoretical calculations indicate that bubble clouds with void fraction of O(1%) and size of O(20 cm) produce large scatter due to collective oscillations. It is suggested that artificial bubble cloud targets can be used for acoustical remote sensing of ocean environment. The flow following property of such targets is excellent because the target density is quasineutral buoyant. The void fraction, bubble size distribution, and cloud geometry can be controlled. A technique using polymer solutions to stabilize bubble clouds was developed. Resonant tube measurements indicated that the acoustic velocity and attenuation of artificial clouds are similar to bubble clouds in water. This technique can be applied to the designs of underwater acoustic targets for sonar calibration, simulation of wave breaking, and neutral buoyant tracers for tracking ocean currents. The use of artificial bubble clouds targets is specially valuable for low wind condition and applications in deeper regions where bubbles generated at the surface rarely survive. Larger bubbles can also be transported into deeper regions by artificial clouds. [Work supported by ARPA.]