ACOUSTIC RADIATION FORCE ON A RIGID SPHERE IN THE NEAR-FIELD OF A CIRCULAR PISTON VIBRATOR

The acoustic radiation force exerted on a rigid sphere whose time-averaged center is at any specified point on the axis of a circular piston vibrator was investigated theoretically including points in the near zone of the radiation with a view to applying it to the absolute measurement of ultrasonic intensity. The velocity potential of incident waves in the near field was expressed in the form of an infinite series of spherical surface harmonics, thereby allowing the use of the conventional scattering theory to calculate the radiation force. The theoretical framework has the advantages that it includes neither approximations nor numerical integrations, and that it is applicable to elastic or compressible sphere cases with slight modifications of the boundary conditions. © 1990, Acoustical Society of America. All rights reserved.