Study On The Acoustic Radiation Force Of Cylindrical Particles Near The Interface

Acoustic radiation is from a variety of physical phenomena,such as absorption and scattering,as well as the changes in the energy density of the acoustic waves due to the scattering,diffraction and reflection of other objects and the interface.The technique of manipulating micro particles by using acoustic radiation forces is called acoustic manipulation.Acoustic manipulation could be widely applied in the fields of material science,ultrasonic medicine and biophysics.Moreover,it is one of the hot topics in the field of acoustics.The core of the acoustic manipulation is the control of the acoustic radiation force,which can be used to manipulate and capture micro particles.So it is important to study the acoustic radiation for the development of acoustic manipulation.The study of acoustic radiation force is mainly focused on the spherical and cylindrical particles and the assumption that the particles are located in an infinite region.The influence of interface on acoustic radiation force is not considered.Cylindrical particle is a very typical particle in the practical application.Particles are generally located in bounded space in the actual particle manipulation so the interface will influence on the sound wave.The influence of interface will cause the change of acoustic radiation force for a particle.Based on this,in this paper,the acoustic radiation forces of the rigid cylinder,the liquid cylinder and the elastic cylinder near an impedance boundary immersed in water for plane wave and Gaussian beam wave are analyzed and studied.The main emphasis of our research is the theoretical derivation and numerical simulation of the acoustic radiation force generated by rigid cylinder,liquid cylinder and elastic cylinder near an impedance boundary for Gaussian beam wave.The main contents include the following aspects:1.The expressions of scattering coefficients of rigid cylinder,liquid cylinder and elastic cylinder near an impedance boundary immersed in water for plane wave and Gaussian beam wave are derived and given based on the acoustic wave theory,which laid the foundation of the further study of acoustic radiation force.2.The expression of the acoustic radiation force on the cylinder near an impedance boundary immersed in water for plane wave is derived based on the theory of acoustic scattering and the addition theorem of cylindrical functions incorporating the method of images.The effects of impendence boundary,the distance-to-radius and the radius of cylinder on acoustic radiation force are analyzed.The results show that:With the increase of the reflection coefficient,the acoustic radiation force functions of rigid cylinder and elastic cylinder decrease,but the oscillation phenomenon is more and more obvious.The acoustic radiation force function of the liquid cylinder is negative and positive depending on the selection of ka.The radiation force changes rapidly and the peaks and dips of acoustic radiation force function become more densely packed with the growth of distance-to-radius.The resonance peaks of acoustic radiation force shift to the low frequencies when the radius of cylinder is increased.3.The expression of the acoustic radiation force of the cylinder near an impedance boundary immersed in water for on-axial Gaussian beam wave is derived and given.The effects of impendence boundary,the distance-to-radius,the radius of cylinder and the distance-to-source on acoustic radiation force are analyzed when the particle is located at the center of the beam with the beam waist is equal to wavelength.The results show that:The acoustic radiation force increases with the increase of beam waist,but its amplitude decreases gradually.The variation of acoustic radiation force versus ka are different.When ka is larger,the acoustic radiation force of cylinder decreases with the increases of ka.The acoustic radiation force of cylinder is smaller than that of the cylinder in the plane wave field when the ka is certain.4.Expressions of axial radiation force and transverse acoustic radiation force of the cylinder near an impedance boundary immersed in water for off-axial Gaussian beam wave are derived.The acoustic radiation force and the variation of an off-axial cylinder near an impedance boundary immersed in water for off-axial Gaussian beam wave are analyzed based on the numerical analysis.The results show that:The effects of impendence boundary on axial acoustic radiation force for the off-axial cylinder are consistent with that for the on-axial cylinder,but the amplitudes and the curves versus ka are different.The transverse acoustic radiation forces of other materials off-axial particles decrease when the ka is small,but they increase when the ka is larger.The axial radiation force function and the transverse acoustic radiation force function on a particle change rapidly and the peaks and dips of them become more densely packed with the growth of distance-to-radius.The distribution of axial radiation force on a particle located at any position relative to the center of the beam is symmetry of y0/a=0.The distribution of transverse radiation force on a particle is symmetry of particle center.The axial radiation force and the transverse acoustic radiation force tend to zero when the particle entirely leaves the beam domain.With the increases of the beam waist,the axial radiation force increases and the transverse acoustic radiation force decreases.