Acoustic radiation force of an incident cylindrical diverging wave exerted on a multilayered sphere is theoretically and numerically studied. Based on sound scattering theory, a closed-form of the acoustic radiation force is obtained and several numerical simulations are provided. It shows unexpectedly that the radiation force becomes negative at selected values of ka and kr₀ in a cylindrical diverging progressive wave (where k is the wave number, a is the sphere's radius and r₀ is the distance of the sphere from the acoustic source). As kr₀ increases to infinity, it degenerates to the case of a plane wave field. Relative thickness of layer affects both magnitude and position of the resonant peaks for a two-layered sphere while it does not significantly affect those for a three-layered sphere. As the innermost layer is substituted by the air, the resonant peaks become more pronounced due to the large difference of acoustic impedance. This study is expected to provide a theoretical basis to develop a new generation of acoustic tweezers using a single beam of progressive waves, which has potential applications in biomedical ultrasound and material sciences.

Based on scattering theory of sound waves, beam factor of a Gaussian beam is obtained with series expanding theory. Analytical expression of acoustic radiation force on a spherical particle near an impedance boundary is deduced. Numerical simulations of rigid and fluid particles are carried out and comparison with those in free space is made. Effects of reflecting coefficient, distance between particle and boundary and waist radius on acoustic radiation force are discussed. It shows that the acoustic radiation force increases along with reflecting coefficient of the boundary, while the peaks are not changed. At some appropriate frequencies, negative acoustic radiation force can be obtained. The acoustic radiation force changes periodically with the distance between particle and boundary. Moreover, the waist radius mainly affects acoustic radiation force at middle and high frequencies. As the particle off-axis distance and angle deviation increases, attenuation of acoustic radiation force becomes obvious. This work provides a theoretical basis for particle manipulation using Gaussian beam.