Particle dispersion in turbulent sedimentary duct flows

Particle behavior in a turbulent pipe flow with a flat bed

“…Generally, in the pipe, the 5μm particles do not move with the secondary flow with their behavior dictated by coherent turbulent structures. The larger 50μm particles tend to deposit on the floor as noted above and as studied in previous work (Liu et al, 2021a(Liu et al, , 2021b. A stable structure of particle distribution in the crosssection cannot be found due to the effects of gravity, with the motion of most particles directed downwards and unlikely to move upwards under the influence of the secondary flow (Liu et al, 2021a).…”

“…7(d)). It is known (Liu et al, 2021b) that the upper wall is 2.42 times longer than the length of the floor and that the upper vortices tend to circulate throughout the whole higher regions of the pipe (Fig. 5) which is quite different from that occurring in a rectangular duct with large aspect ratio (Noorani, et al, 2016).…”

“…It is noted that the distance from the streamline centers of the upper vortices to the corner is 2.68 times that from the centers of the lower vortices to the corner, and the ration of the distance to the adjacent wall is 2.62. Therefore, although the streamline centers of the lower vortices are much closer to the corner and the wall under the wall restriction (Liu et al, 2021a(Liu et al, , 2021b, the vorticity center does not have this property. This is because the vorticity field depends on the near-wall turbulence structure, and the length of the adjacent wall has no significant effect on vorticity (Vinuesa et al, 2014(Vinuesa et al, , 2016.…”

“…As used in Liu et al (2021b), the pipe with flat bed is defined as a circular tube with radius R, where the lower regions of the pipe are occupied by deposited particles.…”

“…Part of the mesh at the center of the pipe is folded (highlighted in the inset of the figure), and the upper mesh line has two overlapping nodes. Such grid generation depends on solution of the Poisson equation (Liu et al, 2021b), which may diverge if overlapping nodes are used as a boundary condition. To obtain an effective solution, the layer above (η = 2) has its grid shape designed as rectangle.…”