### ASA 125th Meeting Ottawa 1993 May

## 4pPA8. The acoustic interaction forces between two fluid spheres in an
acoustic field.

**Xiaoyu Zheng
**

**
Robert E. Apfel
**

**
**
*Ctr. for Sonics and Ultrasonics, P. O. Box 2159, Yale Univ., New Haven, CT
06520
*

*
*
An object in a sound field will scatter the incident wave and experience
the so-called acoustic radiation force, which is a nonlinear time average
effect associated with the incident wave. When two objects are present, the
total acoustic radiation force on either object will include the interaction
portions due to the other's scattered field of the primary wave. The acoustic
interaction force between two fluid spheres in a plane wave field is
investigated by calculating the force on one sphere, which is assumed to be
small compared to the center distance between them. Using the method of Yosioka
[K. Yosioka and Y. Kawasima, Acustica 5, 167--173 (1955)], a general formula
for the radiation force on one sphere is derived that shows dependence on the
resonant modes of the other. It is noted that in the radiation force expression
there are cross terms involving the primary plane wave and scattered wave. For
two small bubbles, this result is the same as the Bjerknes force expression
that is obtained by others under the approximation of very long wavelength.
Calculations are also done for the case of a standing wave field. [Work
supported by NASA through JPL Contract No. 958722.]