纤维表面气溶胶粒子对流扩散沉积行为随机模拟

Stochastic simulation of convective diffusional deposition of ultrafine particles on surface of fibers

采用离散随机模拟方法模拟平行排列纤维表面超细气溶胶粒子的对流扩散沉积过程。以Kuwabara流场近似描述纤维附近区域流体的绕流特征,基于格子随机游走方法求解粒子对流扩散输运方程,以获得粒子在计算区域的运动概率。讨论纤维表面粒子沉积形成粉尘层的动态过程和粉尘层的形态结构特征与粒子输运机制的关系。研究结果表明:粉尘层的形态结构主要依赖于粒子的输运机制,以扩散输运机制主导(多因素归一参量Pe<10)的粒子沉积过程将形成更为开放、松散的粉尘层结构;粒子沉积过程表现出粉尘黏附、粉尘树枝桥接和滤饼生长3个阶段;依据粉尘层填充率随粉尘层厚度的变化关系,粉尘层可分为滤饼基层、滤饼主体层和滤饼表层3个典型结构。

A discrete stochastic model was developed to simulate the convective diffusional deposition of ultrafine particles in a model filter composed of an array of identical parallel fibers placed transverse to the flow. The flow feature in the vicinity of fibers was described by the Kuwabara flow field. Lattice walk method was employed to solve convection-diffusion-migration equation in order to obtain the probability of particle motion in the calculation domain. The local structures of dust layer formed by deposited particles and the relationship between structure of dust layer and mechanisms of particle transport were investigated. The results show that for Pe10, when the diffusion is a controlling mechanism of particles transport, dust layer is more open and looser structure than that obtained at the higher value of Pe. The whole particles deposition process may be distinguished by three stages of particles adhesion, particles bridging and dust layer growth. According to the change of locate packing density along the dust layer height direction, the structure of dust layer can be divided into three typical parts of substructure, main profile and surface layer.