Abstract Previous research has mostly been focused on the drag force in fluid-particle assemblies. However, when the particle geometry is non-spherical, secondary forces and torque may no longer be negligible. In this study particle-resolved simulations are performed to study the drag force, other secondary forces, and torque in flow through a fixed random suspension of ellipsoidal particles with sphericity (ψ = 0.887). The incompressible Navier-Stokes equations are solved using the Immersed Boundary Method (IBM). The suspension of ellipsoidal particles is simulated for solid fraction between 0.1 and 0.35 using 191 to 669 particles, respectively, at low to moderate Reynolds numbers (10 ≤ Re ≤ 200). The results show that the mean drag and lift force and torque with flow incidence angle follow trends similar to that found for isolated particles. However, there are large variations in these quantities under the same conditions of Reynolds number, void fraction, and incidence angle which become more significant as the Reynolds number increases, leading to the conclusion that local flow conditions in the suspension have a large impact on forces and torques experienced by a particle. Secondary lift and lateral forces are compared to the drag force on each particle at the same Reynolds number and solid fraction. The results show that approximately 80% of particles for lift and 60% for lateral force exhibit values 10% (17% for lift and 50% for lateral force) as the Reynolds number increases, leading to the conclusion that neglecting secondary forces could lead to inaccuracies. The mean value of torque coefficient increases with void fraction and decreases with Reynolds number. However, torque on individual particles at the same mean flow conditions show large variations about the mean, even acting in the opposite direction to that indicated by the mean value.

中文翻译：

---

椭球体悬浮液中阻力、升力和扭矩的变化

摘要 以前的研究主要集中在流体-粒子组件中的阻力。然而，当颗粒几何形状为非球形时，次级力和扭矩可能不再可以忽略。在这项研究中，进行了粒子分辨模拟，以研究流过具有球形度 (ψ = 0.887) 的椭圆体粒子的固定随机悬浮液中的阻力、其他次级力和扭矩。不可压缩的 Navier-Stokes 方程使用浸入边界法 (IBM) 求解。在低至中等雷诺数 (10 ≤ Re ≤ 200) 下，分别使用 191 至 669 个颗粒模拟了固体分数介于 0.1 和 0.35 之间的椭圆体颗粒悬浮液。结果表明，平均阻力和升力以及扭矩与流动入射角的趋势与孤立粒子的趋势相似。然而，在雷诺数、空隙率和入射角相同的条件下，这些量有很大的变化，随着雷诺数的增加，这些变化变得更加显着，从而得出结论，悬浮液中的局部流动条件对力有很大的影响和粒子所经历的扭矩。在相同的雷诺数和固体分数下，将次级升力和侧向力与每个颗粒上的阻力进行比较。结果表明，随着雷诺数的增加，大约 80% 的升力粒子和 60% 的横向力表现出 10%（升力为 17%，横向力为 50%）的值，得出的结论是忽略次级力可能导致不准确。扭矩系数的平均值随着空隙率的增加而增加，随着雷诺数的增加而减少。然而，