The evolution of nanoparticles due to Brownian coagulation in the temporal mixing layer with AK-iDNS over a long time

Abstract

In this article, the evolution of nanoparticles in a two-dimensional temporal mixing layer over a long time is investigated. the flow field is calculated with direct numerical simulation (DNS), while the particle field is simulated using the average kernel method coupled with iterative direct numerical simulation (AK-iDNS). Under moderate Reynolds number, the flow field undergoes processes of vortex emergence, entrainment, rolling and pairing, merging, and dissipation. Due to the small Stokes number of nanoparticles, and the particles moves closely following the flow field. Meanwhile, the particle undergoes coagulation under the influence of Brownian motion. This article discusses the evolution nanoparticle under the combined effect of advection, diffusion and coagulation. Under the influence of vortices or large-scale coherent structures, the spatial distribution of particle moments is similar to the structure of the flow field. And diffusion and coagulation have a significant impact on the amplitude of the distribution of particle moments. However, diffusion has little impact on the mean distribution, while coagulation has a much greater impact on the mean distribution. As the flow field evolves, the temporal mixing layer degenerates into Couette flow. The particles exhibit similar asymptotic behavior as that of 0-dimensional problem.