Particles in wall turbulence
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The overall objective of this doctoral thesis is to investigate how tiny particles are dispersed in a turbulent channel flow and how the fluid turbulence is modulated due to the presence of particles. Both spherical and prolate spheroidal particles are considered in present work and their translational and rotational motions are described in a Lagrangian framework using point-particle approximation. The turbulence of the fluid phase is obtained by means of direct numerical simulation (DNS). Accounting for the feed-backs from the particles onto the flow field, a novel scheme of torque-coupling has been developed and implemented together with the more conventional force-coupling in current program. In the case of spherical particle Reynolds number effect on particle velocity statistics and Stokes number effect on the particle slip velocity have been explored in dilute suspension flow with one-way coupling approach. The study on turbulence modulations by spherical particles has been carried out in two-way coupled simulations. The effects of Stokes number and particle volume fraction have been mainly investigated and the mechanisms of particle-turbulence interaction were elucidated by kinetic energy transfer and particle induced dissipation between particle phase and local fluid phase. In the case of prolate spheroidal particle both torque-coupling and force-coupling has been applied in the simulations of particle suspension turbulent shear flow in which the turbulence modulations and particle orientations and spins have been examined. Some results on the comparison of Lagrangian approach and statistical approach in simulating the particle suspensions were presented.
Has partsAndersson, Helge Ingolf; Zhao, Lihao. Computation of particle-laden turbulent flows. Proceedings of The 23rd Nordic Seminar on Computational Mechanics, 2010.
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Zhao, Lihao; Andersson, Helge Ingolf. Two-way coupled simulations of particle-laden wall turbulence. , 2011.
Zhao, Lihao; Andersson, H.I.. On particle stress in gas-solid channel flows. .
Zhao, Lihao; Andersson, Helge I.; Gillissen, Jurriaan J. J.. Interphasial energy transfer and particle dissipation in particle-laden wall turbulence. Journal of Fluid Mechanics. (ISSN 0022-1120). 715: 32-59, 2013. 10.1017/jfm.2012.492.
Andersson, Helge; Zhao, Lihao. DNS of Non-Spherical Particles in Turbulent Flows. , 2010.
Zhao, Lihao; Andersson, H.I.; Gillissen, J.J.J.. Comparison of Lagrangian approach and statistical approach in simulation of fiber suspension turbulent channel flow.. .
Andersson, Helge I.; Zhao, Lihao; Barri, Mustafa. Torque-coupling and particle-turbulence interactions. Journal of Fluid Mechanics. (ISSN 0022-1120). 696: 319-329, 2012. 10.1017/jfm.2012.44.