Scaling behaviours in settling process of fractal aggregates in waterW. J. Tian1, T. Nakayama2, J. P. Huang1 and K. W. Yu3
1 Surface Physics Laboratory and Department of Physics, Fudan University - Shanghai 200433, China
2 Department of Applied Physics, Hokkaido University - Sapporo 060-8628, Japan
3 Department of Physics and Institute of Theoretical Physics, Chinese University of Hong Kong - Shatin, New Territories, Hong Kong, China
received 22 February 2007; accepted in final form 4 April 2007; published May 2007
published online 3 May 2007
We investigate the effect of permeant flow on the sedimentation of porous fractal-aggregates in water. Our theoretical analysis gives explicit calculations on the scaling behaviours of settling velocities, taking into account the fractality through a proper permeability for fractal aggregates. The calculated results for the scaling behaviours of settling velocities fit remarkably well with experimental data. The analytic expression for the settling velocity provides a criterion for determining fractal dimensions Df of aggregates from sedimentation experiments.
61.43.Hv - Fractals; macroscopic aggregates (including diffusion-limited aggregates) .
47.57.-s - Complex fluids and colloidal systems .
92.20.Vn - Sedimentation .
© Europhysics Letters Association 2007