RESEARCH PAPERS: Radiative Properties

Radiative Properties of Numerically Generated Fractal Soot Aggregates: The Importance of Configuration Averaging

[+] Author and Article Information
Fengshan Liu, Gregory J. Smallwood

Institute for Chemical Process and Environmental Technology, National Research Council, Building M-9, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada

J. Heat Transfer 132(2), 023308 (Dec 09, 2009) (6 pages) doi:10.1115/1.4000245 History: Received December 01, 2008; Revised February 26, 2009; Published December 09, 2009; Online December 09, 2009

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multisphere Mie-solution method. The fractal aggregates investigated in this study contain 10–600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame-generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm, and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

The first six realizations for N=100

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Figure 2

Comparison of nondimensional aggregate absorption cross section

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Figure 3

Comparison of nondimensional aggregate total scattering cross section

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Figure 4

Nondimensional vertical-vertical differential scattering cross sections for different aggregate realizations and N=100 and 400

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Figure 5

Scattering phase functions for different aggregate realizations and N=100 and 400

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Figure 6

Variation of configuration- and orientation-averaged CVH(0 deg) with aggregate size N




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