Study On The Acoustic Radiation Force Of Gaussian Beam On Disk Particles

Sound wave has a certain energy, and at the same time micro-particles in the sound field will be affected by acoustic waves, and this kind of affection is called acoustic radiation force. Through the affection of acoustic radiation force, the capture and manipulation of the micro-particles (such as atoms, organelles, DNA, etc.) can be achieved. The study of the Gaussian on micro-particles is always a hot topic both at home and abroad because it plays an essential part in life sciences, materials science, medicine, chemistry, ultrasonic medicine, and many other fields of science. Most of the researches on micro-particles in recent years have focused on the spherical and cylindrical particles, but in the field of acoustic radiation of applied science, there also exists disc and other particles, and the researches on it are relatively few. Based on this fact, the thesis is carried out with two steps. Firstly, under the ellipsoid coordinate system, through the method of scattering and the scattering sound field of disc particles in the sound field from the incident Gaussian beam is solved. Secondly, the Gaussian wave in the acoustic radiation is theoretically deduced. The main contents are as follows:(1)According to the relationship between the oblate spheroidal wave function in the oblate spheroidal coordinate system and spherical harmonics function in the spherical coordinate system, through the limited series expansion of the plane wave in the spherical coordinate system, the author replaces spherical harmonics function with the oblate spheroidal wave function and finally deduces the limited series expansion of the plane wave in the oblate spherical coordinate system. At the same time, according to the limited series expansion of the Gaussian wave in the spherical coordinate system, the factors of the Gaussian wave in the spherical coordinate system are calculated, and then the limited series expansion of the Gaussian wave in the oblate spherical coordinate system is deduced. Meanwhile, the simulation toward them is implemented respectively. The simulation results show that the the limited series expansion of plane wave through shallow spherical coordinates the limited series expansion using analytic and finite series expansion methods, which has the same results with the application of Gaussian. It also shows that in the oblate spherical coordinate system, the result of the limited series expansion of the plane wave and the analytic expression of the plane wave are same, which is in line with the same result of the of Gaussian wave. So it is feasible for the limited series expansion of the Gaussian wave and the plane wave in the oblate spheroidal coordinate system to replace spherical harmonics function with the oblate spheroidal wave function.(2) According to the principle that micro-particles will be affected by sound field in the Gaussian wave sound field, and it can produce scattered waves. Under the theory of acoustic wave, the thesis focuses on studying the scattering situation of the disk, rigid disc and the fixed rigid disc via fluid medium liquid under incident Gaussian wave respectively, and then obtaining expression of scattering coefficient in the oblate spheroidal system when the boundary conditions are different on the basis of the boundary condition of different particles and different solving equations. The results lay a solid foundation for further research on the acoustic radiation force of disc particle.Based on the acoustic radiation theory, the oblate spheroidal wave function in the oblate spherical coordinates is substituted so that the expression of the acoustic radiation force of the plane of rigid disc and the expression of the acoustic radiation force of the Gaussian wave can be deduced. Through the numerical simulation, the effects of the frequency and beam width on the acoustic radiation force are studied. The simulation results show that the acoustic radiation of disc particles in Gaussian sound field is related to the frequency of the sound wave of particles and beam width. When the beam width is larger than wavelength, Gaussian beam can be seen as the plane wave, and the rule that the acoustic radiation force of varies from ka is basically identical with the plane wave. As the frequency of sound wave reaches to 2.5 the radiation force will turn to its maximum; when the ka value is beteween 1 and 1.5 the radiation force will change slowly; when ka changes from 1.5 to 2.5 and it will change quickly.