论文标题
粘度对梗塞液滴中表面声波驱动的集体颗粒动力学的影响：星云，黑洞和白色矮人
Effect of viscosity on surface acoustic wave driven collective particle dynamics in sessile droplets: nebula, black holes and white dwarfs
论文作者
论文摘要
表面声波（SAW）可以在几秒钟内将微粒集中在液滴中。然而，该机制尚不清楚，现有的解释失败了几个数量级。在本文中，我们分析了流体粘度和粒径对液滴中锯驱动的集体颗粒动力学的影响。在我们的大多数实验中，颗粒不会聚集，而是远离液滴中心，从而形成“黑洞”。我们表明，黑洞是由于空间的障碍所致，其中应将颗粒驱动到液滴中心的poloidal流线离固体太近，因此沿着这些流线携带的颗粒触及黑洞边缘的固体壁，然后到达液滴的中心。这些黑洞的大小与粘液较少的液滴形成的聚集体的大小相关。这表明了黑洞和白矮人（聚集体）的常见形成机制。在前者中，触摸固体的颗粒将被流体洗掉，而在后者中，颗粒将与固体接触并滚动到形成聚集体的液滴中心。我们还讨论了液滴底部的聚集体的稳定性条件。然后，使用10 $μ$ m珠作为盾牌，使用流体动力屏蔽的概念将1 $ $ m颗粒浓缩。
Surface acoustic waves (SAW) can concentrate micro-particles in droplets within seconds. Yet, the mechanism is not clear and existing explanations fail by several orders of magnitude. In this paper, we analyze the effect of fluid viscosity and particle size on SAW-driven collective particle dynamics in droplets. In most of our experiments, the particles do not aggregate but instead remain away from the droplet center, thereby forming "black holes". We show that the black holes are due to steric hindrance wherein the poloidal streamlines that should drive particles to the center of the droplet come too close to the solid, so that the particles carried along these streamlines touch the solid wall on the edge of the black hole before reaching the center of the droplet. The size of these black holes is correlated with the size of the aggregates formed in less viscous droplets. This suggests a common formation mechanism for black holes and white dwarfs (aggregates). In the former, the particles touching the solid would be washed away by the fluid, whereas in the latter the particles would remain in contact with the solid and roll to the center of the droplet where an aggregate is formed. We also discuss the stability conditions of the aggregate at the bottom of the droplet. The concept of hydrodynamic shielding is then used to concentrate 1 $μ$m particles using 10 $μ$m beads as shields.
