AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Fractal Scaling of Soot Packing Density across Five Size Decades
PAI LIU, William Heinson, Rajan Chakrabarty, Washington University in St. Louis
Abstract Number: 591 Working Group: Aerosol Physics
Abstract Fractal aggregates in nature grow with a scaling dimensionality less than the spatial dimension. This results in their packing density (θf, solid matter volume fraction) to decrease with increasing size Rg/a (aggregate radius of gyration normalized by average radius of monomers (repeating subunits)). Fundamental questions remain regarding the scaling laws and physical mechanisms controlling the evolution of θf, especially after the onset of gelation. In this work, we experimentally map the scaling of θf for soot aggregates across five orders of magnitude of Rg/a. The θf-Rg/a scaling relationship evolves through three successive regimes with distinct power-law exponents of -1.20±0.01, -0.58±0.06, and -1.31±0.14. The first cross-over agrees with the classical aerosol-to-gel transition theory. This agreement, however, breaks down at the second cross-over point, where a late-stage cluster-cluster aggregation of aerosol gels takes over.