Turbulent Diffusion of Inertial Particle Pairs Such as in Pollen and Sandstorms

We explore the concept of local and non-local diffusion processes [Malik N. A., PLoS ONE 12(12): e0189917 (2017)] in application to the diffusion of inertial particle pairs in the limit of Stoke’s drag. Inertial particles are arguably more important than fluid particles because most real world applications are related to inertial particle motion, from hail and pollen to sandstorms. The inertial pair diffusion regimes depend upon the local Stokes’ number St(l), where l is the pair separation distance. For the inertia dominates and we observe ballistic motion for inertial pair separation. For, the turbulent energy dominates the diffusion process which asymptotes to the fluid non-local pair regime for very large inertial ranges. A numerical model, Kinematic Simulations, is used to generate inertia particle trajectories and we observe the predicted inertial pair diffusion regimes in the limit of large inertial subranges.