Particle concentrations and settling in environmental flows

The motion of particles (dust, droplets, aersols etc) in the atmosphere is influenced both by gravitational settling and turbulence. The particles often also have non-negligible inertia, and this, together with gravitational settling and their interactions with the turbulent air flow leads to very rich and complex motion. One problem that we are working on is understanding how particle inertia, settling, and turbulence compete to control the concentration profiles of the particles in the atmospheric boundary layer. A representation publication on this work is:

A.D. Bragg, D.H. Richter, G. Wang, Mechanisms governing the settling velocities and spatial distributions of inertial particles in wall-bounded turbulence, Physical Review Fluids, 6, 064302, 2021.

Related to the problem of their concentration profiles is how fast the particles settle through the atmosphere. For this we are developing new theoretical tools and performing extensive Direct Numerical Simulations to understad the complex ways in which turbulence modifies the particle settling speeds compared to their settling speeds in quiescent flows. A representation publication on this work is

J. Tom, A.D. Bragg, Multiscale preferential sweeping of particles settling in turbulence, Journal of Fluid Mechanics, 871 244--270, 2019.


This work is supported by the NASA Weather and Atmospheric Dynamics program.