Abstract:
Based on acoustic theory, the Gaussian beam is expanded with cylindrical wave function at the center of the cylinder and the expanded coefficients of the incident Gaussian beam is calculated. The analytical expression for acoustic radiation force on the cylindrical particles induced by the Gaussian beam is deduced. The variation of acoustic radiation force affected by the frequency, the beam waist of the Gaussian beam and the offset distance from the Gaussian beam center are investigated by numerical simulations.The results show that in the case ka<1 the acoustic radiation force is negative when the offset distance is positive.the acoustic radiation force is positive when the the offset distance is negative.for ka>1 the value of the radiation force gradually decreases with the offset distance,and the direction of the radiation force is along the positive direction of x-axis. Moreover, the acoustic radiation force increases with the width of beam, and when the beamwidth is larger than the wavelength(W0=10λ) , the radiation force of the Gaussian beam is close to the value of the plane wave.
KeyWords:
Gaussian beam; offset distance; cylindrical particles; beam width; acoustic radiation force在声场作用下，液体中的微小粒子会受到声辐射力的作用\[1-4\]，利用声波的辐射力实现微小粒子的操控对于声波在生物医学领域的应用具有重要意义.在高斯声场中，目标粒子的辐射力特性一直是研究的热点.文献\[5\]利用散射波的简化表达式,研究了聚焦高斯波束的声辐射力特性，并在以后的研究中证明,利用聚焦波束的声辐射力可以实现粒子的捕获.Mahdi Azarpeyvand等人用积分法研究了聚焦高斯波束对刚性柱的辐射力特性，得出辐射力随离轴距离的变化关系\[6\]，文献\[7-9\]深入地研究了零阶、高阶贝塞尔波束作用下的声辐射力特性, 并得出高斯声波的展开系数对声辐射特性具有一定影响的结论.高斯声波作为超声学应用中非常重要的一种声波分布形式，在高斯波束作用下目标的声辐射力特性研究一直受到国内外学者的普遍关注\[10-12\].目前，有关高斯波束对粒子声辐射力的研究中，通常假设粒子位于入射波的波束中心，但在实际应用中，偏离波束中心粒子所受的声辐射力对于微小粒子的声操控具有重要的意义\[13-14\].本文以声波理论为基础，将高斯波束用有限级数展开，研究水中柱形粒子的位置偏离高斯波束中心时粒子的声辐射力特性，并讨论波束宽度、偏离波束中心距离等参数对声辐射力特性的影响.
