The interaction between particles and turbulent flow is investigated by simultaneous measurement of the time-resolved three-dimensional (3D) velocity of particles and the carrier liquid phase. The investigation is conducted in a horizontal channel flow at a Reynolds number, Re, of 20 000, based on the average velocity and full channel height. The particle-laden suspension is produced by nearly neutrally buoyant beads with a density of $1.05\mathrm{g}/\mathrm{c}{\mathrm{m}}^3$ and a mean diameter of 370 μm at a volumetric concentration of $0.1\%$. The liquid phase is seeded with 2 μm tracers, the images of which are digitally separated from the larger beads using a medina filter, and processed using time-resolved 3D particle tracking velocimetry. Conditional sampling of the beads and their surrounding fluid, based on the beads’ wall-normal motion, showed that ascending beads were mostly located within ejection motions of the fluid. However, the descending beads did not indicate any correlation with the streamwise fluid velocity; the beads were surrounded by wallward fluid motions with both positive and negative streamwise velocity fluctuations. For both ascending and descending beads, the surrounding fluid motion had a strong spanwise velocity component. Inspection of the 3D beads’ pathlines showed a spiral motion of beads around a streamwise axis. At $y/h<0.2$, the descending beads showed a stronger correlation with their surrounding fluid, while ascending beads demonstrated a stronger correlation with their surrounding flow farther away from the wall. Conditional sampling of the beads and their surrounding flow was also performed based on the streamwise acceleration of the beads. The results showed that, in the near-wall region of $y/h<0.2$, slip velocity and the resultant drag force were not in the same direction as the bead acceleration. Therefore, for this near-wall region, the drag force is not sufficient to model the dynamics of the large nearly buoyant beads.

中文翻译：

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湍流通道内颗粒周围三维流动的实验研究

通过同时测量粒子的时间分辨三维（3D）速度和载体液相，研究了粒子与湍流之间的相互作用。根据平均速度和全通道高度，在水平通道中以雷诺数Re为20000进行研究。载有颗粒的悬浮液是由密度为$1.05\mathrm{G}/\mathrm{C}{\mathrm{米}}^3$ 体积浓度为370μm $0.1％$。液相用2μm示踪剂播种，使用麦地那过滤器将其图像与较大的珠子进行数字分离，并使用时间分辨3D粒子跟踪测速仪进行处理。基于珠子的壁法向运动，对珠子及其周围的流体进行有条件的采样显示，上升的珠子大部分位于流体的喷射运动中。但是，下降的珠子与流向流体速度没有任何相关性。珠子被沿壁向的流体运动所包围，同时沿正向和负向的流速波动。对于上升珠和下降珠，周围的流体运动都有很强的翼展速度分量。对3D珠的路径线的检查显示，珠围绕流轴呈螺旋运动。在$ÿ/H<0.2$，下降的珠子与周围的流体表现出更强的相关性，而上升的珠子与远离壁的周围流体表现出更强的相关性。还基于珠的流向加速度对珠及其周围的流进行条件采样。结果表明，在近壁区域$ÿ/H<0.2$，滑动速度和所产生的拖曳力与胎圈加速度的方向不同。因此，对于该近壁区域，拖曳力不足以对大的近浮珠的动力学进行建模。