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FIGURE 5.10 Aggregate properties as a function of size for lake water suspensions and measurements by Amos and Droppo32 for (a) density and (b) porosity. Bars represent the observed range of data.

dimensions are used. In this case, the fractal dimensions obtained from Experiment Set 2, corresponding to the three different measurement times, were incorporated in the calculations (D2 = 1.84,1.75, and 1.65, and D3 = 2.77,2.62, and 2.47, for t = 10min, 20 min, and 30 min, respectively). As expected, the effects of shear rate and differential sedimentation were much greater than the effects of Brownian motion. Furthermore, except for the largest particles, the impact of shear rate was greater than differential sedimentation.

Noting that the fractal dimensions decreased with time, it is seen that j generally increased with time during these experiments. The increase is particularly evident for colliding particles larger than about 100 jxm, where nearly an order of magnitude

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