Date of Award
Doctor of Philosophy
In a turbulent channel flow, an initially uniform distribution of particles evolves into a non-uniform distribution. In a straight turbulent channel, both turbulent eddies and turbophoresis are responsible for the non-uniform distribution. In a curved channel, the dominant cause is particle inertia, but turbulent diffusion still plays an important role. Particulate dispersion in an infinite serpentine channel is studied using direct numerical simulation coupled with Lagrangian particle tracking. Particle Stokes numbers range from 0.125 to 6.0. Above the lowest Stokes number, particles form into a plume that leaves the inner bend at the entrance of the curved section. Turbulence then disperses the plume. Heavier particles move across the channel and reflect from the outer bend, forming a high concentration layer near the outer wall. The heaviest particles reflect again from the wall and are dispersed across the channel by turbulence. An empirical formula is used to analyze the propensity for particle impacts to erode the channel walls. The region of the maximum erosion is neither where the number of impacts is the largest nor where the impact velocity is the highest. The impact angle determines where the erosion is the largest. Instantaneous distributions show that particles with small Stokes numbers accumulate in streaks near the wall, but particles with large Stokes numbers tend to form puffs in the middle of the channel and have less tendency to cluster into wall streaks.
Huang, Xin, "Particulate dispersion in a turbulent serpentine channel" (2011). Graduate Theses and Dissertations. 12137.