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Radiative properties of numerically generated fractal soot aggregates : the importance of configuration averaging
; Liu, Fengshan
Smallwood, Gregory J.
NRC Institute for Chemical Process and Environmental Technology (ICPET-ITPCE); National Research Council Canada
Journal of heat transfer
Fractal aggregates; Soot; Optical properties; Configuration averaging
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. Orientationaveraged
radiative properties of a single aggregate realization are not always sufficient
to represent the properties of random-oriented ensemble of fractal aggregates.