近壁泊肃叶流中活性粒子迁移规律研究

研究活性粒子在剪切流中的迁移规律对实现颗粒分离和过程强化均具有重要意义.基于耗散粒子动力学理论,建立了描述微通道内近壁泊肃叶流中活性粒子迁移运动的数学模型,考察了活性粒子圆周运动角速度、手性诱导角速度、直行运动速度和转向扩散系数对大肠杆菌和常规活性粒子横向迁移速度和受迫转向频率的影响规律,并确定近壁剪切流中活性粒子横向迁移的形成机制.结果表明,近壁剪切流场中大肠杆菌的横向迁移速度随剪切速率增大先快速增加继而趋于稳定;大肠杆菌横向迁移速度随圆周运动角速度增大而减小,随手性诱导角速度、直行运动速度和转向扩散系数的增大而增大;大肠杆菌的受迫转向频率受圆周运动角速度、直行运动速度和转向扩散系数的影响小,而随手性诱导角速度的增大而加快;相比大肠杆菌,常规活性粒子横向迁移速度显著减小、受迫转向频率明显变慢,二者受直行运动速度和转向扩散系数的影响规律与大肠杆菌类似.直行运动是活性粒子形成横向迁移运动的前提,其他运动参数和结构参数均可一定程度促进或抑制活性粒子在近壁剪切流场中的横向迁移.

STUDY ON TRANSPORT OF ACTIVE PARTICLES IN POISEUILLE FLOW NEAR WALL

Mastering the migration principle of active particles under shear flow is of great significance for realizing particle separation and process intensification. Based on the theory of dissipative particle dynamics, a mathematical model describing the migration of active particles in Poiseuille flow near wall in microchannels is established. The effects of the circular angular velocity, chirality-induced angular velocity, self-propulsion velocity and rotational diffusion coefficient on the lateral migration velocity and forced tumble frequency of Escherichia coli and conventional active particles are investigated. Meanwhile, the formation mechanism of the lateral migration of active particles in the shear flow near wall is determined. The results show that the lateral migration velocity of Escherichia coli in the shear flow near wall increases rapidly at first and then stabilizes with the increase of shear rate. The lateral migration velocity of the Escherichia coli decreases with the increase of circular angular velocity, and increases with the increase of chirality-induced angular velocity, self-propulsion velocity and rotational diffusion coefficient. The forced tumble frequency of Escherichia coli is less affected by the circular angular velocity, self-propulsion velocity and rotational diffusion coefficient but increases with the increase of the chirality-induced angular velocity. In contrast with the Escherichia coli, the lateral migration velocity of the conventional active particles is significantly reduced, and the forced tumble frequency is significantly slower. Both the lateral migration velocity and the forced tumble frequency of the conventional active particles are affected by the self-propulsion velocity and rotational diffusion coefficient in a similar way to that of Escherichia coli. The forward locomotion is the precondition for the formation of lateral migration of active particles, while other kinematic parameters and structural parameters can have promotion or inhibition effect on the lateral migration of active particles under shear flow near wall to some extent.