Clustering characteristics of heated bidispersed particles*

Inertial particles tend to cluster in a turbulent flow due to the centrifugal force exerted by the vortices. While the efficiency of numerous state-of-the-art applications of heated particle-laden flows, such as metal powder combustion in satellite engines and solar collectors, heavy rely on the homogeneous dispersion of particles. Conventionally, the ratio of particle response time to the turbulent timescale (known as Stokes number, St) is used to characterize particle distribution. Here, St = 1 corresponds to maximum particle clustering. Intuitively, it seems reasonable to control particle St for uniform dispersion. Yet, practical applications not only contain a range of particle sizes which correspond to different turbulent timescales, but in a turbulent flow St varies with the evolution of timescales. Furthermore, it was recently reported that heating of bidispersed particles create clouds of high viscosity gas in the flow field. These clouds capture and retain smaller particles, and therefore depict higher clustering even at St<1. However, this study was one-way coupled in momentum, whereas particles can modulate turbulence based on their volume fraction/size. Thus, this research is extended by conducting direct numerical simulations with two-way momentum coupling. Here, a significantly higher decay rate of turbulent kinetic energy is observed which reduced the clustering of smaller particles at later timesteps. On the other hand, the clustering of larger particles was unaffected by the change in momentum coupling.