论文标题
在剪切的粗糙颗粒剪切悬浮液模型中流体动力摩擦的参数化
Parameterization of hydrodynamic friction in a model for sheared suspensions of rough particles
论文作者
论文摘要
我们提出了一种方法，以参数化粗粒模型，以在几乎接触悬架流中的粗糙球之间进行流体动力学摩擦。由于表面粗糙度引起的摩擦电阻主要改变了粗糙颗粒运动的滑动和滚动模式。使用近场成对电阻模型的Stokesian动力学模拟，用于计算这些增强的摩擦模式，以计算剪切流中的颗粒轨迹。在此模型中，对滑动和滚动运动模式的阻力是从弱差异的log $（1/h）$形式的平滑球中增强的，以使$ 1/h $形式的强度差异为$ 1/h $形式，以解决由于表面上的平均表面分离之间的表面上的平均表面分离而导致的额外阻力，而$ h $之间的平均表面分离。我们使用不等性约束对不同运动模式的抗性的相对大小确定了新的界限，这反映了一对粗糙颗粒的Stokes抗性张量的正面确定性。使用剪切流中的粒子对的模拟，对剪切中心线的角度旋转速率进行了简单模型，这是其在剪切流中的取向的函数，以及流体动力抗性模型的自由参数：摩擦耦合强度，$α$和摩擦耦合范围，$ H__0 $。然后，可以通过将模型中的对旋转速率与实验观测值相匹配时，可以推断出$α$和$ h_0 $的值，而当稀释的粗糙颗粒悬架受到线性剪切流量时，可以推断出对实验观测。同一模型用于计算对粗粒子悬浮液的高频粘度的流体动力贡献。对于不同的$α$和$ h_0 $，我们观察到粘度的不同而不同，具体取决于$ h_0 $。
We propose a method to parameterize a coarse grained model for the hydrodynamic friction between nearly touching rough spheres in suspension flows. The frictional resistance due to surface roughness primarily alters the sliding and rolling modes of motion of rough particles. Stokesian dynamics simulations incorporating a near-field pairwise resistance model accounting for these enhanced frictional modes were employed to compute particle trajectories in shear flow. In this model, the resistance to sliding and rolling modes of motion are augmented from a weakly diverging log$(1/h)$ form for smooth spheres to a strongly diverging $1/h$ form for rough spheres to account for the additional resistance due to squeezing flows between surface asperities, where $h$ is the mean surface separation between particles. We determine new bounds on the relative magnitude of the augmentations to the resistance to different modes of motion using inequality constraints reflecting the positive definiteness of the Stokes resistance tensor for a pair of rough particles. Using the simulations of a particle pair in a shear flow, a simple model for angular rotation rate of the pair centerline is computed as a function of its orientation in the shear flow and the free parameters of the hydrodynamic resistance model: the friction coupling strength, $α$, and friction coupling range, $h_0$. Values of $α$ and $h_0$ for real-world rough particles can then be inferred by matching the pair rotation rate in the model to experimental observations when a dilute rough particle suspension is subjected to a linear shear flow. The same model is used to calculate the hydrodynamic contribution to the high frequency viscosity of rough particle suspensions. For different $α$ and $h_0$, we observe that the viscosity diverges differently depending on $h_0$.
