Nonspherical Particle Measurement: Shape Factor, Fractals, and Fibers

Aggregated particles caused by instrument artifact

“…3), similar to those observed from several wildfires in Chakrabarty et al (2014) and from a laboratory fire in Kearney and Pierce (2012). Superaggregates tend to have larger mobility diameters than smaller particles; however, they have low aerodynamic diameters (a measure of their terminal settling velocity), lower effective densities, and are more porous, causing different behavior than primary particles or smaller aggregates (Chakrabarty et al, 2014;Kulkarni et al, 2011a). In Chakrabarty et al (2014), superaggregates were collected in the third stage of an aerosol impactor with a cut point of < 0.3 µm aerodynamic diameter (D a ).…”

“…Branched-chain particles with internal voids between branches and compact aggregates with internal voids have mass equivalent diameters that are less than the volume equivalent diameter, which implies lower densities than an equivalent ideal spherical particle (Kulkarni et al, 2011a). Soot particles are fractal-like, chain aggregates produced from incomplete combustion (Kulkarni et al, 2011a;Wang et al, 2017). Large-scale, turbulent fires provide vortices where soot aggregates (∼ 100 s of monomers) can be trapped in a high particle to volume area, creating superaggregates consisting of thousands of monomers (Chakrabarty et al, 2014;Kearney and Pierce, 2012;Kulkarni et al, 2011a).…”

“…When primary particles collide and stick together, agglomerates or aggregates can form, creating complex structures (Kulkarni et al, 2011a). Agglomerate particles can be categorized as branched-chain or compact aggregates (Kulkarni et al, 2011a).…”

“…Soot particles are fractal-like, chain aggregates produced from incomplete combustion (Kulkarni et al, 2011a;Wang et al, 2017). Large-scale, turbulent fires provide vortices where soot aggregates (∼ 100 s of monomers) can be trapped in a high particle to volume area, creating superaggregates consisting of thousands of monomers (Chakrabarty et al, 2014;Kearney and Pierce, 2012;Kulkarni et al, 2011a).…”

“…Agglomerate particles can be categorized as branched-chain or compact aggregates (Kulkarni et al, 2011a). Branched-chain particles with internal voids between branches and compact aggregates with internal voids have mass equivalent diameters that are less than the volume equivalent diameter, which implies lower densities than an equivalent ideal spherical particle (Kulkarni et al, 2011a).…”