Calculation and analysis on axial acoustic radiation force of a Bessel beam on sphere particles

Calculation and analysis on axial acoustic radiation force are very important for the understanding of the movement and trapping of small objects The axial acoustic radiation force of fluid sphere and elastic sphere illuminated by Bessel wave calculated by Partial Waves Series (PWS) is studied.By means of the harmonic expansion of Bessel beam and the scattering form function of sphere particles,the expression of the axial acoustic radiation force can be derived.Through the inspection of scattering form function of different scattering angle,the scattering into backward hemisphere is significantly depressed in the Bessel beam case where the acoustic radiation force Yp is negative.The effects of the thickness ratio and materials of double layers fluid sphere are analyzed.Meanwhile,through series of combinations of materials and thickness for elastic sphere and elastic shell,a wider frequency range and higher magnitude of negative Y_p could be achieved,and the radiation force of elastic sphere may be affected by the resonance of sphere elastic modes.