Article contents
Dispersion of inertial particles in cellular flows in the small-Stokes, large-Péclet regime
Published online by Cambridge University Press: 17 September 2020
Abstract
We investigate the transport of inertial particles by cellular flows when advection dominates over inertia and diffusion, that is, for Stokes and Péclet numbers satisfying $St \ll 1$ and $Pe \gg 1$. Starting from the Maxey–Riley model, we consider the distinguished scaling $St \, Pe = O(1)$ and derive an effective Brownian dynamics approximating the full Langevin dynamics. We then apply homogenisation and matched-asymptotics techniques to obtain an explicit expression for the effective diffusivity $\bar {D}$ characterising long-time dispersion. This expression quantifies how $\bar {D}$, proportional to $Pe^{-1/2}$ when inertia is neglected, increases for particles heavier than the fluid and decreases for lighter particles. In particular, when $St \gg Pe^{-1}$, we find that $\bar {D}$ is proportional to $St^{1/2}/(\log ( St \, Pe))^{1/2}$ for heavy particles and exponentially small in $St \, Pe$ for light particles. We verify our asymptotic predictions against numerical simulations of the particle dynamics.
JFM classification
- Type
- JFM Papers
- Information
- Copyright
- © The Author(s), 2020. Published by Cambridge University Press
References
REFERENCES
- 2
- Cited by