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.]