Impact of morphology on the radiative properties of fractal soot aggregates

Doner N., Liu F.

JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, cilt.187, ss.10-19, 2017 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 187
  • Basım Tarihi: 2017
  • Doi Numarası: 10.1016/j.jqsrt.2016.09.005
  • Dergi Adı: JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.10-19
  • Anahtar Kelimeler: Overlapping, Aggregate expansion, Fractal soot aggregates, Aerosol optical properties, DDA, DISCRETE-DIPOLE APPROXIMATION, ABSORPTION CROSS-SECTION, OPTICAL-PROPERTIES, ELECTROMAGNETIC SCATTERING, LIGHT-SCATTERING, SIMULTANEOUS COAGULATION, PARTICLES, SIMULATION, PARAMETERS
  • Gazi Üniversitesi Adresli: Hayır

Özet

The impact of morphology on the radiative properties of fractal soot aggregates was investigated using the discrete dipole approximation (DDA). The optical properties of four different types of aggregates of freshly emitted soot with a fractal dimension D-f=1.65 and a fractal pre-factor k(f)=1.76 were calculated. The four types of aggregates investigated are formed by uniform primary particles in point-touch, by uniform but overlapping primary particles, by uniform but enlarged primary particles in point-touch, and formed by point touch and polydisperse primary particles. The radiative properties of aggregates consisting of N=20, 56 and 103 primary particles were numerically evaluated for a given refractive index at 0.532 and 1.064 mu m. The radiative properties of soot aggregates vary strongly with the volume equivalent radius a(eff) and wavelength. The accuracy of DDA was evaluated in the first and fourth cases against the generalized multi-sphere Mie (GMM) solution in terms of the vertical-vertical differential scattering cross section (C). The model predicted the average relative deviations from the base case to be within 15-25% for C-w depending on the number of particles for the aggregate. The scattering cross sections are only slightly affected by the overlapping but more significantly influenced by primary particle polydispersity. It was also found that the enlargement of primary particles by 20% has a strong effect on soot aggregate radiative properties. (C) 2016 Elsevier Ltd. All rights reserved.