Eulerian-Eulerian Modeling of Turbulent Gas-Particle Flow

Doktorsavhandling, 2009

Gas-particle flow is encountered in a vast number of industrial operations and natural phenomena. Computational fluid dynamics plays an important role in practical engineering and fundamental research activities. For the numerical prediction of gas-particle two-phase flow, an Eulerian approach is employed in this work so as to describe the particulate-phase as a continuum medium with properties analogous to those of a fluid. In addition, kinetic theory of granular flow is used to derive closure relations that take into account particle-particle interaction and interstitial fluid effects. Two-way coupling considers momentum transfer from the dispersed particulate-phase to the continuous gas-phase through appropriate source terms in the momentum and turbulent kinetic energy conservation equations. A modified k-ε model is used to estimate the continuous phase turbulence. Balance of kinetic energy associated with particle random motion and the correlation between fluid-and-particle fluctuating velocity are also incorporated. Friction plays an important role in determining gas-particle flow at very high particulate-phase concentration, so the development of a frictional stress model is also discussed. The derived two-phase flow model is used for the prediction of dilute turbulent gas-particle flow in a backward-facing step and a cold CFB-riser. The study of dense particle flow restricts to the formation of a cavity in a granular bed by an impinging turbulent jet. Closure models are implemented in a commercial CFD software, and simulation results are thoroughly validated with available experimental data.