Numerical Modeling of Turbulent Gas-Particle Flow
Licentiate thesis, 2007
This work presents a theoretical and numerical study of gas-particle two-phase flow within the Eulerian framework. Although gas-particle flows have been extensively studied, there is still no general agreement on the constitutive equations for an Eulerian-Eulerian model in which the dispersed phase is treated as a continuum, i.e. a granular fluid. To successfully simulate the averaged behavior of a gas-particle flow system, it is necessary to account for the fluctuating motion present in each phase. Kinetic theory of granular flow is commonly employed to derive appropriate dispersed phase properties in which the mean kinetic energy associated with particle velocity fluctuations plays a major role. In addition, collisions are considered as an important means of momentum and energy transfer within the dispersed phase. The influence of the interstitial gas on the particulate phase constitutive relations is also taken into account. It is shown that interphase coupling terms arise from the decomposed and averaged transport equations. The equations for mean quantities are used to introduce the closure models, mainly for the fluctuating kinetic energy relative to each phase. This is a more fundamental approach than assuming a standard k-ε model, with additional heuristic terms, as employed in most research work on turbulent gas-particle flow. As a result, attention is devoted to the influence of turbulence on dispersed phase mean quantities and turbulence modulation. Numerical simulations of fully developed turbulent gas-particle flow in a vertical pipe and a backward-facing step are validated with benchmark experimental measurements.