The propulsion of colloidal particles via planar traveling ultrasound waves has attracted increasing attention in recent years. A frequently studied type of particles is bullet-shaped and cup-shaped nano- and microparticles. Based on acoustofluidic simulations, this article investigates how the propulsion of bullet-shaped particles depends on their length and diameter, where cup-shaped particles are included as limiting cases corresponding to the smallest particle length. The structure of the flow field generated by the particles is discussed and it is shown that the particles' propulsion strength increases with their length and diameter. When varying the diameter, we observed also a sign change of the propulsion. This work complements previous experimental studies that have addressed such particles only for particular aspect ratios, and the provided understanding of how the propulsion of the particles depends on their dimensions will prospectively be helpful for the choice of particle shapes that are most suitable for future experimental studies.

中文翻译：

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通过行进的超声波推进子弹形和杯形纳米和微粒

近年来，通过平面行进超声波推进胶体颗粒受到越来越多的关注。一种经常研究的颗粒类型是子弹形和杯形纳米和微粒。基于声流体模拟，本文研究了子弹形颗粒的推进如何取决于它们的长度和直径，其中杯形颗粒被包括作为与最小颗粒长度相对应的限制情况。讨论了颗粒产生的流场结构，表明颗粒的推进强度随着它们的长度和直径的增加而增加。当改变直径时，我们还观察到推进力的符号变化。这项工作补充了以前的实验研究，这些研究仅针对特定纵横比处理此类粒子，