Abstract Hydrodynamics of rod-like particles, found extensively in the chemical and process industry, is investigated here, using direct numerical simulations. A recently developed formulation of the smoothed profile method for rigid bodies is first validated for rod-like particles (rods) and then used to characterize the concentration effects on the static and dynamic properties of rods in the Stokes regime. Normalized drag and lift coefficients of a single rod of aspect ratio 3 and 4, followed the well known sin2θ and sin θ cos θ curves against the incident angle (θ), respectively. We found significant inhomogeneity in the microstructure of the settling rods. These inhomogeneties, cause the formation of clusters, even at low volume fractions. These clusters move as a large lump, inducing pronounced hydrodynamic interactions, which have significant effects on the settling system. The average settling velocity normalized by the terminal velocity of an isolated rod, shows a non-monotonic behavior; increasing at low concentration because of the cluster formation in which rod packets settle faster than an isolated rod, and decreasing at high concentration because of many particle interactions. Furthermore, velocity fluctuations are larger than those of spherical particles because of the cluster formation. Histogram of particles’ orientation angle shows that the majority of the particles are vertically aligned.

中文翻译：

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用光滑剖面法对棒状颗粒沉降的数值研究

摘要 这里使用直接数值模拟研究了广泛存在于化学和加工工业中的棒状粒子的流体动力学。最近开发的刚体平滑轮廓方法的公式首先针对棒状粒子（棒）进行验证，然后用于表征 Stokes 状态下棒的静态和动态特性的浓度效应。纵横比为 3 和 4 的单个杆的归一化阻力和升力系数分别遵循众所周知的 sin2θ 和 sin θ cos θ 曲线与入射角 (θ) 的关系。我们发现沉降棒的微观结构存在显着的不均匀性。即使在低体积分数下，这些不均匀性也会导致簇的形成。这些簇作为一个大块移动，引起明显的流体动力学相互作用，对沉降系统有显着影响。由孤立杆的终端速度归一化的平均沉降速度显示出非单调行为；由于团簇形成，其中杆包比孤立的杆沉降得更快，因此在低浓度下增加，而在高浓度下由于许多粒子相互作用而减少。此外，由于团簇的形成，速度波动大于球形颗粒的速度波动。粒子取向角的直方图显示大部分粒子垂直排列。由于团簇形成，其中杆包比孤立的杆沉降得更快，因此在低浓度下增加，而在高浓度下由于许多粒子相互作用而减少。此外，由于团簇的形成，速度波动大于球形颗粒的速度波动。粒子取向角的直方图显示大部分粒子垂直排列。由于团簇形成，其中杆包比孤立的杆沉降得更快，因此在低浓度下增加，而在高浓度下由于许多粒子相互作用而减少。此外，由于团簇的形成，速度波动大于球形颗粒的速度波动。粒子取向角的直方图显示大部分粒子垂直排列。