Aggregation chaotic flows

We focus on aggregation in model, regular and chaotic, flows. Two aggregation scenarios are considered In (i) the clusters retain a compact geometry—forming disks and spheres—whereas in (ii) fractal structures are formed. The primary focus of (i) is kinetics and self-similarity of size distributions, while the main focus of (ii) is the fractal structure of the clusters and its dependence with the flow. 

Illustration Aggregation in chaotic flows with constant capture radius. 

Here we consider aggregation in a physically realizable chaotic flow, the journal bearing flow or the vortex mixing flow described earlier. The computations mimic fast coagulation particles seeded in the flow are convected passively and aggregate upon contact. In this example the clusters retain a spherical structure and the capture radius is independent of the cluster size. 

Illustration Aggregation of area-conserving clusters in two dimensional chaotic flows. Particles, converted passively in a two-dimensional chaotic flow, aggregate on contact to form clusters. The capture radius of the clusters increases with the size of the cluster. Since these simulations are in two dimensions, the area of the aggregating clusters is conserved. 

Illustration Aggregation of fractal structures in chaotic flows. In a... 

Hansen, S., Aggregation and fragmentation in chaotic flows of viscous fluids. Ph.D. Thesis, Northwestern University (1997). 

Illustration Aggregation of fractal structures in chaotic flows. In a further study of aggregation in two-dimensional chaotic flows, the passively convected clusters retain their geometry after aggregation, i.e., fractal structures are formed. A typical fractal cluster resulting from these simulations is shown in Fig. 41. 

Ottino, J.M., Unity and diversity in mixing stretching, diffusion, breakup, and aggregation in chaotic flows, Phys. Fluids, A, 3/5, 1417-1430, 1991. 

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