The acoustic radiation force produced by ultrasonic waves is the “workhorse” of particle manipulation in acoustofluidics. Nonspherical particles are also subjected to a mean torque known as the acoustic radiation torque. Together they constitute the mean acoustic fields exerted on the particle. Analytical methods alone cannot calculate these fields on arbitrarily shaped particles in actual fluids and are no longer fit for purpose. Here, a semi-analytical approach is introduced for handling subwavelength axisymmetric particles immersed in an isotropic Newtonian fluid. The obtained mean acoustic fields depend on the scattering coefficients that reflect the monopole and dipole modes. These coefficients are determined by numerically solving the scattering problem. Our method is benchmarked by comparison with the exact result for a subwavelength rigid sphere in water. Besides, a more realistic case of a red blood cell immersed in blood plasma under a standing ultrasonic wave is investigated with our methodology.

中文翻译：

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施加在亚波长轴对称粒子上的平均声场

超声波产生的声辐射力是声流体学中粒子操纵的“主力”。非球形颗粒也受到称为声辐射扭矩的平均扭矩。它们一起构成了平均声场施加在粒子上。单独的分析方法无法计算实际流体中任意形状的粒子的这些场，并且不再适用。在这里，介绍了一种半解析方法来处理浸入各向同性牛顿流体中的亚波长轴对称粒子。获得的平均声场取决于反映单极子和偶极子模式的散射系数。这些系数是通过数值求解散射问题来确定的。我们的方法通过与水中亚波长刚性球体的精确结果进行比较来进行基准测试。此外，使用我们的方法研究了一个更真实的红细胞在驻波下浸入血浆中的情况。