Dense suspensions of solid particles in viscous liquid are ubiquitous in both industry and nature, and there is a clear need for efficient numerical routines to simulate their rheology and microstructure. Particles of micron size present a particular challenge: at low shear rates, colloidal interactions control their dynamics while at high rates, granular-like contacts dominate. While there are established particle-based simulation schemes for large-scale non-Brownian suspensions using only pairwise lubrication and contact forces, common schemes for colloidal suspensions generally are more computationally costly and thus restricted to relatively small system sizes. Here, we present a minimal particle-based numerical model for dense colloidal suspensions that incorporates Brownian forces in pairwise form alongside contact and lubrication forces. We show that this scheme reproduces key features of dense suspension rheology near the colloidal-to-granular transition, including both shear thinning due to entropic forces at low rates and shear thickening at high rates due to contact formation. This scheme is implemented in LAMMPS, a widely used open source code for parallelised particle-based simulations, with a runtime that scales linearly with the number of particles, making it amenable for large-scale simulations.

中文翻译：

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使用接触力、润滑力和布朗力的成对公式模拟稠密悬浮液的流变学

粘性液体中固体颗粒的密集悬浮液在工业和自然界中普遍存在，显然需要有效的数值程序来模拟其流变学和微观结构。微米尺寸的颗粒提出了一个特殊的挑战：在低剪切速率下，胶体相互作用控制其动力学，而在高剪切速率下，颗粒状接触占主导地位。虽然已经建立了仅使用成对润滑和接触力的大规模非布朗悬浮液的基于粒子的模拟方案，但胶体悬浮液的常见方案通常计算成本更高，因此仅限于相对较小的系统尺寸。在这里，我们提出了一个基于最小粒子的致密胶体悬浮液数值模型，该模型将成对形式的布朗力与接触力和润滑力结合在一起。我们表明，该方案再现了胶体到颗粒转变附近的致密悬浮液流变学的关键特征，包括由于低速率熵力引起的剪切稀化和由于接触形成而在高速率下剪切增稠。该计划实施于兰姆普斯，一种广泛使用的开源代码，用于基于粒子的并行模拟，其运行时间随粒子数量线性扩展，使其适合大规模模拟。