Gaseous $\text{SO}_{2}$ entrainment from a contaminated outer air stream into a pair of side-by-side homogeneous and heterogeneous micro-sized water drops is numerically examined for varied gap ratio $0.1\leqslant G/R\leqslant 6.0$ (ratio of interfacial gap to radius), Reynolds number $20\leqslant Re\leqslant 150$ , Weber number $We\leqslant 1.1$ , and liquid-phase Péclet number $58.33\leqslant Pe_{l}\leqslant 1055.56$ . For $20<Re\leqslant 150$ and $0.1\leqslant G/R\leqslant 6.0$ , the separation–attachment induced momentum exchange and imposed non-uniform interfacial shear stress lead to breakup of the primary Hill’s vortex ring and create a significant secondary vortex ring in each drop, which together construct a dominant advective $\text{SO}_{2}$ transport mechanism therein. Beneath a three-dimensional (3-D) topological separation line, the study identifies an active advective mass entrainment process that is led by the ‘inflow’ natured local dynamics of this primary–secondary vortex ring pair. Mechanistically, the secondary and primary vortex rings regulate species transfer into a drop by maintaining the spontaneous inflow-type counter-rotating motion along the 3-D separation line, whereby the $\text{SO}_{2}$ is entrained; and near the attachment points/nodes, two vortices distinctly repulse $\text{SO}_{2}$ entry by virtue of their ‘outflow’ natured local dynamics. The blockage effect and nozzle effect on flow approaching and passing the narrow neck that formed in the presence of a second drop lead to the asymmetric growth of both primary and secondary vortex rings via the locally weakened and enhanced near-interfacial air flow and imposed variable shear stress, which induce the occurrence of an asymmetric mass transfer phenomenon plus biased saturation. The $\text{SO}_{2}$ , once entrained, rotates mostly along a spiral orbit of a primary vortex ring, owing to its higher strength. For increased $Re$ , the $\text{SO}_{2}$ transport process is reinforced following increased strength of the inflow paired secondary–primary vortex dynamics that enhanced the net entrainment rate and also advanced its transport to the vortex core via augmented convective flow plus radial diffusion. A narrow gap facilitated faster near-gap saturation, while the quantitative $\text{SO}_{2}$ transport rate is decreased by virtue of the produced tapered primary–secondary vortex pairs, associated inner flow bifurcation, and changed topology of the separated wake, which appear similar to what develops for a larger single drop. The gap induced inner vortical structures are characterized by a weaker secondary vortex and a tapered primary vortex near the neck. For heterogeneous drop pairs, the influence of varying 3-D surface flow topology on the two interfaces and the impact of solid fraction $0.1\leqslant S\leqslant 0.8$ ( $S=R_{p}/R$ , with $R_{p}$ being the radius of the solid core) on the created advective mechanism by the primary–secondary vortex ring pair and resultant $\text{SO}_{2}$ transport are exclusively elucidated.

数值研究了从污染的外部气流中夹带的气态 $ \ text {SO} _ {2} $ 并入一对并列的均质和非均质微尺寸水滴， 以求出不同的间隙比$ 0.1 \ legslant G / R \ leqslant 6.0 $ （界面间隙与半径的比值），雷诺数 $ 20 \ leqslant Re \ leqslant 150 $ ，韦伯数 $ We \ leqslant 1.1 $ 和液相Péclet数 $ 58.33 \ leqslant Pe_ {l} \ leqslant 1055.56 $ 。对于 $ 20 <Re \ leqslant 150 $ 和 $ 0.1 \ leqslant G / R \ leqslant 6.0 $ ，分离-附着引起动量交换并施加不均匀的界面剪切应力，导致主希尔涡旋环破裂并在每个液滴中形成一个显着的次级涡旋环，这共同构成了主要的对流 $ \ text {SO} _ { 2} $的 传输机制。在三维（3-D）拓扑分离线下，该研究确定了一个主动的对流质量夹带过程，该过程由该“初级-次级”涡流环对的“流入”性质的局部动力学引起。从机械上讲，次级涡流环和初级涡流环通过沿3D分离线保持自发的流入型反向旋转运动来调节物种转移到液滴中，从而 $ \ text {SO} _ {2} $ 被卷入 在附着点/结点附近，两个涡流凭借“流出”的自然局部动力学特性明显排斥 $ \ text {SO} _ {2} $ 进入。阻塞效应和喷嘴效应对流向并通过第二滴形成的狭窄颈部的流动的影响，通过局部减弱和增强的近界面空气流并施加可变剪切力，导致初级和次级涡流环的不对称增长。应力，这会导致不对称传质现象的发生以及饱和度的偏差。的 $ \ {文本SO} _ {2} $ ，一旦夹带，大多沿着主涡环的螺旋轨道，由于其较高的强度旋转。对于增加的 $ Re $ ， $ \ text {SO} _ {2} $ 随着流入的次级-初级涡流动力学强度的增加，输运过程得到加强，从而增强了净夹带率，并通过对流和径向扩散的增强将其输送到涡流核。狭窄的间隙促进了更快的近间隙饱和，而定量 $ \ text {SO} _ {2} $ 由于产生的锥形初级-次级涡流对，相关的内部流分叉以及分离的尾流的变化的拓扑结构，运输速率降低了，这看起来与较大的单滴液滴的发展相似。间隙引起的内部涡旋结构的特征在于较弱的次级涡旋和靠近颈部的锥形初级涡旋。对于异构液滴对，变化的3-D表面流拓扑结构对两个接口的影响以及固体成分的影响 $ 0.1 \ leqslant S \ leqslant 0.8 $ （ $ S = R_ {p} / R $ ，其中 $ R_ {p } $ 是由主次涡环对和所产生的 $ \ text {SO} _ {{2} $ 专门说明了运输方式。