Particle dispersion in turbulent sedimentary duct flows.

[Display omitted] • Dispersion of particles in turbulent sedimentary-duct flows is studied. • Two kinds of eddies forming the secondary flow in the sedimentary duct are found. • Small particles (5 μ m, St = 0.6) move with the secondary flow fully. • Lift force may have significant influence on the behavior of medium particles (10 μ m, St = 2.5). • Drag force dominates the behavior of large particles (50 μ m, St = 63). A simplified geometric model of a circular tube with a sedimentary layer is proposed and named as sedimentary duct. Based on h = 1/4 d (h is the thickness of sedimentary layer and d is the pipe diameter), the flow field (Re = 40000) and particle distribution (5, 10, 50 μ m and St = 0.6, 2.5, 63) in the sedimentary duct are simulated using Large Eddy Simulation (LES) coupled with Lagrange Particle Tracking (LPT) method. As a result, four streamwise eddies are found in the sedimentary duct as distributed in pairs near the corner. The eddy center near ceiling is found to be farther from the corner than that from the floor. Small particles (5 μ m, St = 0.6) tend to move with the secondary flow as their upward movements distribute in both sides. Their centripetal movement is near the floor and preferential distribution near the top. For large particles (50 μ m, St = 63), it is the drag force that dominates their motion while for medium particles (10 μ m, St = 2.5) lift force may have significant influence on their motion. This study is the first work to investigate the characteristics of particle behavior in turbulent sedimentary duct flows. [ABSTRACT FROM AUTHOR]