title: Changes in fractal dimension during aggregation.
abstract: Experiments were performed to evaluate temporal changes in the fractal dimension of aggregates formed during flocculation of an initially monodisperse suspension of latex microspheres. Particle size distributions and aggregate geometrical information at different mixing times were obtained using a non-intrusive optical sampling and digital image analysis technique, under variable conditions of mixing speed, coagulant (alum) dose and particle concentration. Pixel resolution required to determine aggregate size and geometric measures including the fractal dimension is discussed and a quantitative measure of accuracy is developed. The two-dimensional fractal dimension was found to range from 1.94 to 1.48, corresponding to aggregates that are either relatively compact or loosely structured, respectively. Changes in fractal dimension are explained using a conceptual model, which describes changes in fractal dimension associated with aggregate growth and changes in aggregate structure. For aggregation of an initially monodisperse suspension, the fractal dimension was found to decrease over time in the initial stages of floc formation.
authors.affiliation: Department of Civil, Structural and Environmental Engineering, State University of New York at Buffalo, 207 Jarvis Hall, Buffalo, New York 14260, USA. rkc@acsu.buffalo.edu
authors.forename: Rajat K
authors.initials: RK
authors.lastname: Chakraborti
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Gardner
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Atkinson
authors.forename: John E
authors.initials: JE
authors.lastname: Van Benschoten
mesh_terms: D011232:Chemical Precipitation; D017709:Fractals; D008863:Microspheres; D008956:Models, Chemical; D010316:Particle Size; D033081:Shear Strength