Calculation Of The Acoustic Radiation Force Based On The Finite-Difference Time-Domain Method

It is well known that acoustic waves are capable of carrying momentum and energy. An object in a sound field that absorbs or reflects sound energy is subjected to the acoustic radiation force by exchanging momentum and energy with sound wave. Acoustic radiation pressure can control particles without damage and contact. This effect can be applied widely in Cell Biology, Biophysics, Biomedical Engineering and other fields. It has been one of the hot research points for the scientific community and engineering. Profound understanding of acoustic radiation force should be the base for its application in theory. However, theoretical work at this stage is mainly based on scattered wave theory and the algorithm is limited to studying the acoustic radiation force of the spheroid or the columnar which is in the regular sound fields such as plane wave, standing wave, Gaussian beam and so on. In this work, we will induct Finite-Difference Time-Domain (FDTD) to calculate acoustic radiation force. At the same time, we will use this arithmetic to study steel column's acoustic radiation force which is in the vicinity of subwavelength slit in order to get the general law. Specific contents are as follows:Firstly, we study the general theory of three-dimensional (3-D) Finite-Difference Time-Domain method combined with momentum-flux tensor theory which is used for calculating the acoustic radiation force to obtain the acoustic radiation force of steel ball in the plane wave sound field. The result is in good agreement with the scattering wave theory. The algorithm can be used to calculate the acoustic radiation force of particle with any structure, shape and material in any sound field. Meanwhile, it can greatly enhance our theoretical understanding of the acoustic radiation force.Secondly, we study the acoustic radiation force of the steel column on the surface of subwavelength slit structure. As the subwavelength slit is at first-order resonant frequency range, the acoustic radiation force of the steel column is greater than the radiation of seamless structure. Besides, we discuss the affection for the acoustic radiation force peak value by the width and depth of subwavelength slit and the distance between the steel column and joints at first-order resonant frequency range. Theoretical results show that with the decrease of subwavelength slit width, the increase of the depth and the shortening of the distance between the slit and the cylindrical, the peak value of acoustic radiation force will increase. This is in good agreement with the changing trends of the first order resonance frequency of the subwavelength slit. It also shows that enhancement of acoustic radiation force is due to the subwavelength structure. The study of the acoustic radiation force of the steel ball in the subwavelength structure can improve our understanding of FDTD algorithm which is used for calculating the acoustic radiation force, at the same time, it can help us to further understand the acoustic radiation force of particle in special sound field and to provide a theoretical basis of the application of acoustic radiation force.