AI 中文总结
本文通过直接数值模拟研究圆柱绕流中粒子的优先聚集，发现无量纲沉降速度St/Fr²是控制空隙演化的主导参数，重力会改变粒子分布形态，揭示了尾迹动力学、粒子惯性与重力的共同作用机制。
AI 中文摘要
本文对圆柱绕流的粒子负载流动开展直接数值模拟，研究无限长垂直通道流中粒子的优先聚集特性。在雷诺数Re=100和200下，针对不同的粒子斯托克斯数、粒子负载量和弗劳德数开展流动分析，以量化粒子惯性与重力沉降对粒子运动的综合影响。无粒子负载流动在两个雷诺数下均呈现钝体绕流中经典的涡脱模式，观测到雷诺数相关的尾迹宽度、尾迹恢复及速度亏损演化，表征了支配粒子动力学的相干流动结构。在粒子负载的非定常尾迹流中，非均匀粒子分布形成相干空隙与聚集团，其形状与背景流动动力学直接相关。重力改变粒子-流体相互作用，使滑移速度增大，削弱涡诱导的粒子聚集并促使粒子穿过涡，导致空隙形状从单个叶状结构向蛇形空隙区转变，最终形成近垂直空隙结构。在圆柱前方的上游区域，惯性粒子形成弓激波状结构，其范围随斯托克斯数增大和有限弗劳德条件增加而扩大。采用基于沃罗诺伊（Voronoi）的分析结合局部Q值，研究重力与惯性对粒子分布的影响，确定无量纲沉降速度St/Fr²为控制空隙形状演化、归一化空隙单元面积及沃罗诺伊单元面积概率分布的主导参数，报道了尾迹动力学、粒子惯性与重力共同支配钝体尾迹中粒子的优先聚集。
英文摘要
Direct numerical simulations are carried out for particle-laden flow over the cylinder to investigate preferential clustering of particles in an unbounded vertical channel flow. The flow is examined at Reynolds numbers Re=100 and 200 for varying particle Stokes number, particle loadings and Froude numbers to quantify the combined influence of particle inertia and gravitational settling on particle motion. The unladen flow exhibits the classical vortex shedding pattern observed in flow over bluff bodies at both Reynolds numbers. Reynolds number dependent wake width, wake recovery, and velocity-deficit evolution are observed, characterizing the coherent flow structures that govern particle dynamics. In particle-laden unsteady wake flows, the non-uniform particle distribution leads to formation of coherent voids and clusters, whose shape are directly correlated with background flow dynamics. Gravity modifies particle-fluid interaction, which leads to an increase in slip velocity, weakens vortex-induced particle clustering and promotes them to travel through vortices, resulting in a transition of the void shape from individual leaf-like structure to snake-like void zone and eventually into a nearly vertical void structure. In upstream region infront of the cylinder, inertial particles form a bow-shock-like structure whose extent increases with increase in Stokes number and finite Froude conditions. Voronoi based analysis combined with local Q values is used to investigate effect of gravity and inertia on particle distribution. The dimensionless settling velocity, St/Fr^2, is identified as the governing parameter controlling the evolution of void shape, normalized void cell area and the probability distribution of Voronoi cell areas. The effect of wake dynamics, particle inertia, and gravity is reported to jointly govern preferential clustering in bluff-body wakes.
Comments26 pages, 24 figures
