The rheology of concentrated suspensions of particles is complex and typically exhibits a shear-thickening behavior in the case of repulsive interactions. Despite the recent interest arisen, the causes of the shear-thickening remain unclear. Frictional contacts have been able to explain the discontinuous shear thickening in simulations. However, the interparticle friction coefficient is considered to be constant in most simulations and theoretical works reported to date despite the fact that tribological experiments demonstrate that the friction coefficient can not only be constant (boundary regime) but also decrease (mixed regime) or even increase (full-film lubrication regime), depending on the normal force and the relative velocity between the particles and the interstitial liquid between them. Interestingly, the transition between the boundary regime and the full-lubrication regime is governed by the particle average roughness. Particle-level simulations of suspensions of hard spheres were carried out using short-range lubrication and roughness-dependent frictional forces describing the full Stribeck curve. Suspensions with different particle’s roughness were simulated to show that the particle roughness is a key factor in the shear-thickening behavior; for sufficiently rough particles, the suspension exhibits a remarkable shear-thickening, while for sufficiently smooth particles, the discontinuous shear-thickening disappears.

中文翻译：

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用于模拟粗糙多分散颗粒致密悬浮液的摩擦变摩擦系数模型

颗粒浓缩悬浮液的流变学是复杂的，并且在排斥相互作用的情况下通常表现出剪切增稠行为。尽管最近引起了人们的兴趣，但剪切增稠的原因仍不清楚。摩擦接触已经能够解释模拟中的不连续剪切增稠。然而，尽管摩擦学实验表明摩擦系数不仅可以恒定（边界状态）而且可以降低（混合状态）甚至增加，但在迄今为止报道的大多数模拟和理论工作中，颗粒间摩擦系数被认为是恒定的（全膜润滑方式），取决于法向力和颗粒之间的相对速度以及它们之间的间隙液体。有趣的是，边界状态和完全润滑状态之间的过渡由颗粒平均粗糙度控制。使用描述完整 Stribeck 曲线的短程润滑和依赖于粗糙度的摩擦力对硬球悬浮液进行粒子级模拟。模拟了不同颗粒粗糙度的悬浮液，表明颗粒粗糙度是影响剪切增稠行为的关键因素；对于足够粗糙的颗粒，悬浮液表现出显着的剪切增稠，而对于足够光滑的颗粒，不连续的剪切增稠消失。使用描述完整 Stribeck 曲线的短程润滑和依赖于粗糙度的摩擦力对硬球悬浮液进行粒子级模拟。模拟了不同颗粒粗糙度的悬浮液，表明颗粒粗糙度是影响剪切增稠行为的关键因素；对于足够粗糙的颗粒，悬浮液表现出显着的剪切增稠，而对于足够光滑的颗粒，不连续的剪切增稠消失。使用描述完整 Stribeck 曲线的短程润滑和依赖于粗糙度的摩擦力对硬球悬浮液进行粒子级模拟。模拟了不同颗粒粗糙度的悬浮液，表明颗粒粗糙度是影响剪切增稠行为的关键因素；对于足够粗糙的颗粒，悬浮液表现出显着的剪切增稠，而对于足够光滑的颗粒，不连续的剪切增稠消失。