Date of Award
Doctor of Philosophy (PhD)
Ayodeji O. Demuren
The flows of fully-developed turbulent rotating pipe and particle-laden swirling jet emitted from the pipe into open quiescent atmosphere are investigated numerically using Large-Eddy Simulation (LES). Simulations are performed at various rotation rates and Reynolds numbers, based on bulk velocity and pipe diameter, of 5.3x103, 12x103, and 24x103, respectively. Time-averaged LES results are compared with experimental and simulation data from previous studies. Pipe flow results confirm observations in previous studies, such as the deformation of the turbulent mean axial velocity profile towards the laminar Poiseuille-profile, with increased rotation. The Reynolds stress anisotropy tensor shows a redistribution due to pipe rotation. The axial component near the wall is suppressed, whereas the tangential component is amplified, as rotation is increased. The anisotropy invariant map also shows a movement away from the one-component limit in the viscous sublayer, with increased rotation. Exit conditions for the pipe flow simulation are utilized as inlet conditions for the jet flow simulation. Jet flow without swirl and at a swirl rate of S=0.5 is investigated. Swirl is observed to change the characteristics of the jet flow field, leading to an increase in jet spread and velocity decay and a corresponding decrease in the jet potential core. Lagrangian tracking with one way coupling is used to analyze particle dispersion in the jet flow. Three particle diameter sizes are investigated: 10, 100, and 500μm, which correspond to Stokes numbers of 0.06, 6, and 150, respectively. Particles are injected with an initial velocity set equal to the instantaneous fluid phase flow velocities at the jet inlet. The results show that, in the absence of swirl, particle dispersion is inversely proportional to particle size. With the addition of swirl, particle evolution is much more complicated. Largely unaffected by turbulent structures, the largest particles maintain their initial radial trajectory and disperse radially outward significantly more with the addition of swirl. The smaller particles, much more susceptible to turbulent structures, are shown to quickly diffuse within the jet, and their dispersion is unaffected by swirl. With the addition of swirl, dispersion of the midsize particles is shown to increase initially from the jet inlet up to a distance of approximately three diameter lengths downstream. Particle tracking and particle concentration analysis shows that the increase in particle dispersion of the midsize particles upstream is due to an initial outward migration of particles that are injected near the edge of the jet inlet.
Castro, Nicolas D..
"Large-Eddy Simulation of Axially-Rotating, Turbulent Pipe and Particle-laden Swirling Jet Flows"
(2012). Doctor of Philosophy (PhD), dissertation, Mechanical Engineering, Old Dominion University, DOI: 10.25777/mpdk-zd57