Research Computing Seminar – CIRC

About the event

The Center for Institutional Research Computing’s September seminar will be given by Dr. Rohit Dhariwal.

Coffee and light refreshments will be served.

Using Direct Numerical Simulation to Understand the Small-scale Dynamics of Settling, Bidisperse Particles in Turbulence

The motion of small, inertial particles in turbulent flows is a topic of great importance to a large range of problems, such as aerosol manufacturing, drug delivery, spray combustion, and plankton distribution in oceans. It is also of great importance to understanding the formation of clouds in the atmosphere, for which improving our understanding of the role of turbulence on cloud droplet collision rates and mixing could help improve microphysical models of clouds, which often neglect the effect of turbulence. The majority of studies consider mixing and collisions of monodisperse particles, wherein all the particles are physically identical. However, in most real particle-turbulence systems, the particles are polydisperse. In clouds and many other problems, the particle collisions are usually binary due to the dilute particle loading, and furthermore, mixing and dispersion of the particles in the flow is typically analyzed by considering the relative motion of particle-pairs. In this case, the problem of polydispersity reduces to understanding the effect of bidispersity on the small-scale, particle-pair motion. Systematic studies of how bidispersity affects the particle collisions in the presence of gravity, are lacking.

In this talk, I will present results from our direct numerical simulations, to show that the combined influence of turbulence and gravity can have a number of non-trivial effects on the “vertical” (in the direction of gravity) and “horizontal” (i.e. in the plane normal to gravity) relative velocities of settling bidisperse particles. I will also discuss how gravity affects the clustering of monodisperse and bidisperse particles in different ways. Finally, I will consider the implications of these results for the collision rates of settling, bidisperse particles in turbulence.