(80d) Modeling of the Hydrodynamics of Gas–Solid Flows by Improved Finite Volume Based Finite Element Method

Computational fluid dynamics in multiphase flow has become a well accepted and useful tool in modeling of gas/solid flow systems during the recent years, and much progress has been made toward developing computer codes for describing the fluidized beds. In this work computational fluid dynamics of the flow behavior in a cold flow in the riser section of the fluidized bed is studied. An improved finite volume based finite element (FVBFE) method has been introduced to solve the two-phase gas/solid flow hydrodynamic equations. The fluid dynamic model for gas/solid two-phase flow is based on the two-fluid model where both phases are continues and fully interpenetrating. For the gas and solid phases the Navier-Stokes equation based on the concept of local average is obtained [Kuippers 1992]. The FVBFE method uses a collocated grid, where all variables are located at the nodal points. To prevent pressure checkerboard, the objective of this method is to couple between velocity and pressure or porosity in the continuity equation. For this reason we use two types of velocity, convecting velocity (in the continuity equation) and convected velocity (in the momentum equation) [Moraveji, 2004]. In this formulation we use streamline upwind scheme and physical influence scheme and transport equation to represent a new formula of the convected and convecting velocity. The geometry of the riser is similar to the experimental set up used by Yang [1991]. We show the comparison between the calculated radial gas and particle velocities distribution in the riser at heights of 1.6 and 6.6 m with experimental data, prediction of gas/particle phase's velocity vectors, time-averaged axial particle volume fraction and pressure in the riser.