The aims of this work are to elucidate the effects that bulk solids properties have on the effective drag experienced by large spheres immersed in an emulsion of group-B solids under minimum fluidization conditions and to analyze the ways in which the different suspensions react towards different applied shear rates. To investigate this, magnetic particle tracking was applied to resolve the trajectory of falling-sphere measurements in which the size, density, and sphericity of the bulk solids were varied as well as the size and density of the spherical tracers. The resulting experimental scope included both rising and sinking tracers as well as full segregation and in-bed stagnation of the tracers. The set-up provided highly resolved tracer trajectories, from which the drag experienced by the sphere can be calculated. For sinking tracers, the results showed that an increase in bulk solids size, angularity, and density reduced the terminal velocity of the sphere. This effect correlated well with the bed expansion and Hausner ratio, indicating that a reduced void space among the bulk solids is the main reason for the increase in motion resistance. At lower shear rates, namely, during the de-acceleration towards the stagnant state, beds of larger, more angular, or denser bulk solids yield lower levels of shear stress. The angle of repose of the bulk solids correlated with the rate at which the emulsion thins with increasing shear rate. For rising tracers, shear stress did not show any significant dependency on the properties of the bulk solids.

中文翻译：

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最小流化时浸入流化床的球体的有效阻力——散装固体特性的影响

这项工作的目的是阐明在最小流化条件下散装固体特性对浸入 B 组固体乳液中的大球体所经历的有效阻力的影响，并分析不同悬浮液对不同应用的反应方式剪切率。为了研究这一点，应用磁粉跟踪来解决落球测量的轨迹，其中散装固体的大小、密度和球形度以及球形示踪剂的大小和密度是变化的。由此产生的实验范围包括上升和下沉示踪剂以及示踪剂的完全分离和床内停滞。该设置提供了高度解析的示踪剂轨迹，从中可以计算球体所经历的阻力。对于下沉示踪剂，结果表明，散装固体尺寸、棱角和密度的增加会降低球体的最终速度。这种效应与床膨胀和 Hausner 比率密切相关，表明散装固体之间的空隙空间减少是运动阻力增加的主要原因。在较低的剪切速率下，即在向停滞状态减速期间，更大、更有角度或更致密的散装固体床产生较低水平的剪切应力。散装固体的休止角与乳液随剪切速率增加而变稀的速率相关。对于上升示踪剂，剪切应力并未显示出对散装固体特性的任何显着依赖性。这种效应与床膨胀和 Hausner 比率密切相关，表明散装固体之间的空隙空间减少是运动阻力增加的主要原因。在较低的剪切速率下，即在向停滞状态减速期间，更大、更有角度或更致密的散装固体床产生较低水平的剪切应力。散装固体的休止角与乳液随剪切速率增加而变稀的速率相关。对于上升示踪剂，剪切应力并未显示出对散装固体特性的任何显着依赖性。这种效应与床膨胀和 Hausner 比率密切相关，表明散装固体之间的空隙空间减少是运动阻力增加的主要原因。在较低的剪切速率下，即在向停滞状态减速期间，更大、更有角度或更致密的散装固体床产生较低水平的剪切应力。散装固体的休止角与乳液随剪切速率增加而变稀的速率相关。对于上升示踪剂，剪切应力并未显示出对散装固体特性的任何显着依赖性。更多角度或更致密的散装固体产生较低水平的剪切应力。散装固体的休止角与乳液随剪切速率增加而变稀的速率相关。对于上升示踪剂，剪切应力并未显示出对散装固体特性的任何显着依赖性。更多角度或更致密的散装固体产生较低水平的剪切应力。散装固体的休止角与乳液随剪切速率增加而变稀的速率相关。对于上升示踪剂，剪切应力并未显示出对散装固体特性的任何显着依赖性。