### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 3pUW5. A discussion of the low-frequency resonance scattering of a bubble
cloud.

**Paul A. Hwang
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**
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*Res. Div., QUEST Integrated, Inc., 21414 68th Ave. South, Kent, WA 98032
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A comparison of four different formulas to compute the lowest mode
resonance frequency of a bubble cloud is provided in this presentation. Based on
the comparison, it is concluded that only one of the four equations represents
the generalized solution, which includes air bubbles as its asymptotic
condition, of void traction equals unity. Also shown is the numerical
calculation of the scattering of a spherical bubble cloud using the classical
solution of acoustic scattering of elastic spheres. With the elastic properties
of the bubble cloud approximated by Wood's formulation, it is found that
isothermal conditions exist only at a very low void fraction level (less than
0.0001). Within the range of void fraction from 0.001 to 0.1, the polytropic
coefficient of the bubble cloud is approximately 1.2, which is halfway between
adiabatic and isothermal conditions. Finally, two simple scaling laws for the
resonance characteristics of a spherical bubble cloud are presented: (1) the
dimensionless resonance wave number is uniquely determined by the void fraction;
and (2) the backscatter cross section at resonance is uniquely determined by the
resonance frequency. [Work supported by ARPA.]