A computational study on the effect of particle characteristics on the deposition of small particles in turbulent wall-bounded flows

Particle deposition dynamics in a fully developed turbulent channel flow at a friction Reynolds number of Re-tau = 180 for two Stokes numbers (St = 1 and 10) are investigated using the point particle-direct numerical simulation (PP-DNS) method, considering dilute system and thus, one-way coupling. In particular, the interplay between particle size, particle property (density) and deposition at the same Stokes number has been investigated. It turns out that the dimensionless particle relaxation time (the Stokes number) alone does not provide enough information to capture the deposition dynamics, and particle size (diameter) and density need to be considered to obtain a more comprehensive understanding of deposition process. Furthermore, we demonstrate that gravity significantly alter the deposition patterns of particles with different size and density differently, even if the Stokes number does not change, and therefore the results from zero gravity cannot be extrapolated to non -zero gravity settings, even for small particles. Finally, our results suggest that wall -normal particle velocity variance at the wall plays an integral role in the deposition process, as it approaches a finite value (significantly larger than particle mean velocity) at the wall.