【摘要】 由于带电微米颗粒之间存在静电、流体相互作用,颗粒团的迁移行为与单颗粒截然不同。本文以静电除尘器(ESP)中带电颗粒团迁移沉积为背景,首先探讨流体有限惯性对单颗粒扰流流场的影响,在此基础上利用Oseen动力学计算颗粒团迁移过程中的颗粒团形状演化机理。计算发现,在颗粒间流体相互作用下,颗粒团由初始的球形经历扁化、拖尾、破碎等过程,最后形成子颗粒团。随着颗粒荷电量增加,颗粒团迁移由原本的破碎模式转变为较为稳定的各向同性膨胀模式。迁移模式转变能够用荷电参数κ_q定量描述。最后,我们发现颗粒团破碎形式与颗粒初始分布不均匀性有关,并且利用Lyapunov指数定量分析了颗粒团形状不稳定性。更多还原

【Abstract】 Due to the hydrodynamic and electrostatic interactions among micro-particles, the collective behavior of a migrating particle cloud is totally different from that of a single particle. In this paper, the effect of fluid inertia is first discussed based on the analysis of disturbance field of a single particle. Then the evolution of a migrating cloud with both electrostatic and hydrodynamic interactions is numerically investigated by Oseen dynamics. Results indicate, with a weak long-range Coulomb repulsion, the cloud is seen to flatten into a toroidal configuration and eventually breaks up into small clouds. Increasing the repulsion can delay or even totally prevent the breakup. A dimensionless charge parameter, κ_q, is constructed to quantify this transition. Finally, we show that the breakup of the cloud is strongly related to the initial inhomogeneity of the particle concentration.And the chaotic characteristic of the cloud is further quantified by Lyapunov exponent.更多还原