Abstract

We use dynamic numerical simulations to investigate the role of particle rotation in pairwise capillary interactions of particles trapped at a fluid interface. The fluid interface is modeled with a phase-field method which is coupled to the Navier–Stokes equations to solve for the flow dynamics. Numerical solutions are found using a finite element scheme in a bounded two-dimensional geometry. The interfacial deformations are caused by the buoyant weight of the particles, which are allowed to both translate and rotate due to the capillary and viscous forces and torques at play. The results show that the capillary attraction is faster between freely rotating particles than if particle rotation is inhibited, and the higher the viscosity mismatch, the greater the effect. To explain this result, we analyze the drag force exerted on the particles and find that the translational drag force on a rotating particle is always less than its non-rotating counterpart due to attenuated velocity gradients in the vicinity of the particle. We also find that the influence of interfacial deformations on particle rotation is minute.

Graphic Abstract

中文翻译：

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粒子旋转加快了毛细血管的相互作用

摘要

我们使用动态数值模拟来研究颗粒旋转在流体界面处捕获的颗粒的成对毛细管相互作用中的作用。流体界面采用相场方法建模，该方法与Navier–Stokes方程耦合以解决流动动力学问题。使用有限元方案在有限的二维几何中找到了数值解。界面变形是由颗粒的浮重引起的，由于毛细作用和粘性作用以及所产生的扭矩，颗粒的浮重得以平移和旋转。结果表明，自由旋转的颗粒之间的毛细吸引力要比抑制颗粒旋转时更快，并且粘度不匹配越高，效果越好。为了解释这个结果，我们分析了施加在粒子上的阻力，发现旋转粒子上的平移阻力始终小于其非旋转对应物，这是由于粒子附近的速度梯度衰减所致。我们还发现界面变形对粒子旋转的影响很小。

图形摘要