Particle-resolved direct numerical simulations of monodisperse settling suspensions of cubes and spheres are performed for Galileo numbers $\text{Ga}=70$ and $\text{Ga}=160$, and solid volume fractions in the range $0.01⩽\varphi ⩽0.2$. The solid-to-fluid density ratio $m={\rho }_s/{\rho }_f$ is taken to be fixed at 2, representing liquid-solid suspensions. Strong columnar clustering is observed for $\text{Ga}=160$ and $\varphi =0.01$ in a sphere suspension, whereas similar vertical structures are not present as prominently in a cube suspension. We find that in all cases, cube suspensions tend to be more homogeneous compared to sphere suspensions, as indicated by both their microstructure and momentum transfer properties. The enhanced homogeneity is associated with the pronounced angular velocities of cubes and the resulting orientation- and rotation-induced lift forces, which promote transverse motions and the likelihood of escaping from clusters. Higher rotation rates of cubes thus play a major role in the transfer of momentum from the gravity to the transverse direction, demonstrated by the lower anisotropy of particle velocity fluctuations in cube suspensions. In more dilute cases, cubes induce significantly stronger pseudoturbulence in the flow, especially in the transverse direction. The drag of dynamic cube suspensions is found to be generally similar to static beds of cubes, the reason for which is speculated to be relevant to their motion freedom and the more homogeneous microstructure.

中文翻译：

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立方和球形惯性单分散悬浮液的沉降

针对Galileo数，对立方体和球体的单分散沉降悬浮液进行了粒子解析直接数值模拟 $\text{嘎}=70$ 和 $\text{嘎}=160$，以及在该范围内的固体体积分数 $0.01⩽\varphi ⩽0.2$。固液比$米={\rho }_s/{\rho }_F$固定为2，代表液固悬浮液。观察到强柱状聚类$\text{嘎}=160$ 和 $\varphi =0.01$在球形悬架中，类似的垂直结构在立方体悬架中并不显着。我们发现，在所有情况下，立方球体的悬浮液都比球体悬浮液更均匀，这是由其微观结构和动量传递特性所表明的。增强的同质性与立方体的明显角速度以及所产生的取向和旋转引起的升力有关，后者促进了横向运动和从团簇中逃逸的可能性。因此，立方体的较高旋转速率在动量从重力到横向的传递中起主要作用，这由立方体悬架中的粒子速度波动的较低各向异性所证明。在更稀薄的情况下，立方体会在流动中引起明显更强的假湍流，特别是在横向上。发现动态立方体悬架的阻力通常类似于静态立方体床，其原因据推测与它们的运动自由度和更均匀的微观结构有关。