由於近年來化石燃料的大量使用，伴隨而來的即為污染物的排放，其中在硫的部分主要會以氣相的SO2被排放至大氣中，接著SO2會被大氣中的液滴所吸收形成酸雨或酸霧，進而影響環境，因此SO2在液滴中傳輸的過程以及其中的動力行為為本文所探討的主題。
本文首先建立一SO2被雲霧中液滴所吸收之模式，並且以單相模擬法(SPSM)簡化了原本較為複雜的模式，其中探討在三種不同雷諾數下(Reg=0.643、Reg=1.287以及Reg=12.87)物理吸收以及化學吸收之動力行為。物理吸收由於對流效應主導整個吸收過程，因此隨著雷諾數的增加而使得飽和時間縮短，化學吸收則因為化學解離主導了吸收過程，因此儘管雷諾數增加，其飽和時間卻相當的一致。
接著探討SO2被雨滴中之液滴所吸收之現象，在模式上修正了液滴表面之切線速度方程式，始其增加可運用之雷諾數範圍，在本文討論了100μm、200μm、300μm以及400μm之液滴其物理吸收與化學吸收之動力行為。於物理吸收中隨著液滴尺寸的增加，其飽和時間會被拉長，吸收率會增加，濃度的分布會由液滴後方逐漸地往前方達到飽和;在化學吸收中，液滴尺寸增加也會使飽和時間拉長，但吸收率會降低，而濃度則是由液滴表面逐漸地往流線中心達到飽和。

Transient chemical absorption dynamics of sulfur dioxide by a water aerosol droplet in cloud or fog at three Reynolds numbers of 0.643, 1.287 and 12.87 are predicted. In the first part of this research, a sinusoidal velocity distribution at the droplet surface is assumed to approach the flow field inside the droplet and a single-phase simulation method (SPSM) is developed to compare with the two-phase simulation method (TPSM). Considering the physical SO2 absorption processes with internal circulation, the predictions based the SPSM are very close to those of the TPSM, revealing that the SPSM is a proper method to evaluate the mass transport phenomena for SO2 uptake by an aerosol droplet. When chemical reactions in the course of absorption are taken into account using the SPSM, it is noteworthy that the transient absorption process is almost independent of the Reynolds number. This arises from that fact that the entire mass transfer process is controlled by mass diffusion and dominated by the dissociation of sulfurous acid (SO2∙H2O). It is also found that the chemical absorption period is elongated markedly compared to the physical absorption process, approximately by the factors of 5.6-13.1. Eventually, an analysis on the characteristic times of various transport processes is performed to elucidate mass transport mechanisms and the reasonability of the SPSM developed in first part.
A simplified model of predicting chemical SO2 absorption by single freely falling raindrops with internal circulation in the atmosphere is developed in the second part. By multiplying a modification factor α into the model of interfacial velocity established from creeping flow, it is found that the relative error between the simplified model and the two-phase simulation method is less than 4%. Accordingly, the simplified model enables us to simulate the atmospheric SO2 absorption process with less computational effort and without losing accuracy. The simulated results indicate that the dissociation of H2SO3 governs the mass transfer process and the concentration of HSO3- is by far larger than those of SO32- and H2SO3. As a result, the chemical absorption takes a much longer period of time to achieve the uptake process. Specifically, for the raindrop radius in the range of 200-500μm, the absorption time of chemical absorption is larger than that of physical absorption by the factors of 70-290. From the perspective of characteristic time, mass diffusion is the controlling mechanism for SO2 absorption. When chemical absorption is carried out, the absorption period is 28-33 folds of the characteristic time of mass diffusion, implying that the former is always larger than the latter by over an order of magnitude.

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