The Influence of Water Coating on the Optical Scattering Properties of Fractal Soot Aggregates
The Influence of Water Coating on the Optical Scattering Properties of Fractal Soot Aggregates
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DOI：
10.1080/02786826.2011.605401
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发表时间：
2012-01
影响因子：
5.2
通讯作者：
Chao Liu;R. Panetta;P. Yang
中科院分区：
文献类型：
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作者：
Chao Liu;R. Panetta;P. Yang
采用核幔理论和两种有效介质理论的近似方法，研究了组成单体的水涂层对分形烟尘聚集体单散射特性的影响。采用聚类-聚类聚类算法对分形聚集体进行数值生成，采用核-幔广义多粒子Mie （GMM）方法对包水单体烟灰聚集体的单散射特性进行精确计算。然后将GMM方法或Rayleigh-Debye-Gans （RDG）方法与Maxwell-Garnett或Bruggeman有效介质近似（共四种近似方法）相结合的近似所获得的结果进行比较。计算了水包覆分形聚集体的消光和吸收截面、单散射反照率和相矩阵；这些计算是在0.628 μm和1.1 μm两个波长下进行的。分形聚集体的水涂层增加了消光和吸收截面、单散射反照率和前向散射，但降低了后向散射。GMM +麦克斯韦-加内特的组合给出了在涂层厚度和骨料尺寸范围内相当好的近似值。GMM + Bruggeman组合的效果不太好，高估了消光和吸收截面，低估了单散射反照率。在RDG情况下，使用Bruggeman近似是较好的组合，但所涉及的误差大于GMM + Maxwell-Garnett组合。简单理想化计算的结果表明，在吸收性不如烟灰的气溶胶核的情况下，与麦克斯韦-加内特和布鲁格曼近似的结果之间的差异应该更大。美国气溶胶研究协会版权所有
The effect of water coating of constituent monomers on the optical single-scattering properties of fractal soot aggregates is investigated numerically using core-mantle theory and approximations involving two effective medium theories. A cluster–cluster aggregation algorithm is used to numerically generate fractal aggregates, and the core-mantle Generalized Multi-particle Mie (GMM) method is used to compute the exact single-scattering properties of soot aggregates with water-coated monomers. Comparisons are then made with results obtained using approximations that combine either the GMM method or the Rayleigh–Debye–Gans (RDG) method with either the Maxwell-Garnett or the Bruggeman effective medium approximation (a total of four approximation methods). The optical properties calculated are the extinction and absorption cross sections, the single-scattering albedo, and the phase matrix of water-coated fractal aggregates; these calculations are done for two wavelengths, 0.628 μm and 1.1 μm. Water coating of the fractal aggregates is shown to increase the extinction and absorption cross sections, the single-scattering albedo, and forward scattering, but decrease backward scattering. The combination GMM + Maxwell-Garnett gives approximations that are quite good over a range of coating thicknesses and aggregate size. The combination GMM + Bruggeman performs less well, overestimating the extinction and absorption cross sections and underestimating the single-scattering albedo. In the case of RDG, the better combination is with the Bruggeman approximation, but the errors involved are greater than with the GMM + Maxwell-Garnett combination. Results from simple idealized calculations indicate that the differences between results with the Maxwell-Garnett and Bruggeman approximations should be even larger in cases of aerosol cores that are less absorptive than soot. Copyright 2012 American Association for Aerosol Research