12,251 research outputs found
Transition from Knudsen to molecular diffusion in activity of absorbing irregular interfaces
We investigate through molecular dynamics the transition from Knudsen to
molecular diffusion transport towards 2d absorbing interfaces with irregular
geometry. Our results indicate that the length of the active zone decreases
continuously with density from the Knudsen to the molecular diffusion regime.
In the limit where molecular diffusion dominates, we find that this length
approaches a constant value of the order of the system size, in agreement with
theoretical predictions for Laplacian transport in irregular geometries.
Finally, we show that all these features can be qualitatively described in
terms of a simple random-walk model of the diffusion process.Comment: 4 pages, 4 figure
Superdiffusion of massive particles induced by multi-scale velocity fields
We study drag-induced diffusion of massive particles in scale-free velocity
fields, where superdiffusive behavior emerges due to the scale-free size
distribution of the vortices of the underlying velocity field. The results show
qualitative resemblance to what is observed in fluid systems, namely the
diffusive exponent for the mean square separation of pairs of particles and the
preferential concentration of the particles, both as a function of the response
time.Comment: 5 pages, 5 figures. Accepted for publication in EP
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