Aggregate collision radius

Looking at the meaning of Qc in another way, if the hydrodynamic radius of an aggregate is the radius of a sphere that has the same settling velocity and drag force as the aggregate in question, then S2e can be shown to relate the radius of collision to... 

Is in fact constant with aggregate size as implied by Equation (3.38) If it is, then this implies that the hydrodynamic radius is linearly related to the radius of collision, a conclusion that has considerable support in the literature [10, 66]. This would also mean that the dimensionless permeability of the aggregates is also constant with respect to aggregate size, a proposition that has had support recently [67,68]. 

What are the issues relating to the shape of the aggregate, choice of size measurement and to preferential orientations in settling Suppose that instead of the radius of collision of the aggregate we had preferred to use as a size characterization the radius of a sphere having the same projected area as the aggregate, Ra.. The drag force of the system would then be expressed as... 

We now examine the connection between these computer simulations and the Smoluchowski equation. Consider the form of the kernel for aggregation of particles undergoing Brownian diffusion (see Fig. 17), where the diffusion coefficient of a particle of mass / is D,. In the frame of reference of particle /, the diffusion coefficient of particle j is (Z), + Dj). A collision occurs if the center of particle j enters a sphere of radius (r, + rj) around particle /, so [46]... 

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