The Study Of Acoustic Radiation Force Of Spherical Particles In Water By Sound Waves

Acoustic radiation,mainly applied to the micro-manipulation in Acoustics,can realize the manipulation and capture of nano-particles without contact with them.It is also widely used in some interdisciplinary fields such as cell engineering,biomedical engineering,biophysics and materials science,etc.The characteristics of sound field and acoustic radiation can be different owing to the difference in acoustic sources,particles properties and boundary conditions,etc.Thereby,it can be applied in various aspects.Based on a physical model of acoustic radiation force in ideal fluid,this thesis respectively have an in-depth study and calculation about the acoustic radiation force of plane wave,spherical wave and Gaussian beam on hard sphere.It mainly includes the following aspects:Firstly,the author deduces the expression of acoustic radiation pressure on the particles under the Euler-Lagrange Coordinate system in the ideal fluid ignoring viscosity,heat conduction and relaxation in linear acoustics.The plane wave is expanded as spherical function and this thesis respectively discusses the acoustic scattering coefficient of the plane wave on hard sphere,liquid sphere and elastic sphere.According to the superposition principle,the superimposed sound field and sound velocity of a plane wave on the hard sphere is calculated and the expression of acoustic radiation pressure under the Euler-Lagrange coordinate system is also deduced.Through integral operation,the acoustic radiation force of the sound pressure on rigid spherical surface is calculated and it therefore makes a basis for the following study about the acoustic radiation force of spherical wave and Gaussian beam on the spherical particles.Secondly,this thesis discusses acoustic wave equation in spherical coordinate and derives the general solution of acoustic pressure in acoustic field.It tries to evaluate some parameters like sound radiation pressure of pulse spherical sound source in steady state and to discuss the characteristics of point acoustic source.By discussing about how a spherical wave acts on a hard sphere,calculating the scattering coefficient and the superimposed field and making a mathematical treatment and a comparison of plane wave and acoustic field at infinity,the author therefore draws a conclusion that there is a similarity between a spherical wave at infinity and plane wave and it is verified that a spherical wave can be expanded as a spherical function.And then,the author uses spherical Bessel function and spherical Hankel function to complete linear processing for the nonlinear superposition acoustic field,calculates the acoustic radiation force of a spherical wave on a hard sphere and then tries to make a comparison with the the acoustic radiation force on the plane wave.Thirdly,this thesis elaborates the wide application of acoustic radiation force in Nondestructive Testing(NDT)and Biomedicine.Starting with the introduction of Gaussian beam,the Gaussian Beam is then expanded as spherical function and the beam factor of the incident Gaussian Beam is also calculated.After the calculation and discussion,the author comes to a conclusion that the Gaussian beam can be considered as plane wave when the waist radius of Gaussian beam(W0)is considerably large.The relation between the radiation force of sound wave and the waist radius can be deduced through simulating the Gaussian beam with related computer software and calculating acoustic radiation force of Gaussian beam on hard sphere.