Effects of multiple scattering on radiative properties of soot fractal aggregates

• Published in: Journal of quantitative spectroscopy & radiative transfer Vol. 133; pp. 374 - 381
• Main Authors: Yon, Jérôme, Liu, Fengshan, Bescond, Alexandre, Caumont-Prim, Chloé, Rozé, Claude, Ouf, François-Xavier, Coppalle, Alexis
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-01-2014; Elsevier
• Subjects: Aggregates; DDA; Engineering Sciences; Fractal analysis; Fractals; GMM; Light scattering; Mathematical analysis; Multiple scattering; RDG-FA; Scattering; Soot; Soot fractal aggregates; Wavelengths; DDA; Multiple scattering; Light scattering; Soot fractal aggregates; GMM; RDG-FA
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2013.08.022

The in situ optical characterization of smokes composed of soot particles relies on light extinction, angular static light scattering (SLS), or laser induced incandescence (LII). These measurements are usually interpreted by using the Rayleigh–Debye–Gans theory for Fractal Aggregates (RDG-FA). RDG-FA is simple to use but it completely neglects the impact of multiple scattering (MS) within soot aggregates. In this paper, based on a scaling approach that takes into account MS effects, an extended form of the RDG-FA theory is proposed in order to take into account these effects. The parameters of this extended theory and their dependency on the number of primary sphere inside the aggregate (1<Np<1006) and on the wavelength (266nm<λ<1064nm) are evaluated thanks to rigorous calculations based on discrete dipole approximation (DDA) and generalized multi-sphere Mie-solution (GMM) calculations. This study shows that size determination by SLS is not distorted by MS effect. On the contrary, it is shown that fractal dimension can be misinterpreted by light scattering experiments, especially at short wavelengths. MS effects should be taken into account for the interpretation of absorption measurements that are involved in LII or extinction measurements.
•We incorporate multiple scattering effects in a scaling approach for fractal aggregates.•A generalized structure factor is introduced for implementation in RDG-FA theory.•Forward scattering is affected by multiple scattering as well as power law regime.•Absorption cross sections are affected by multiple scattering.•Absorption cross sections are 11% higher than that for forward scattering.