(378a) Development of Filtered Particulate Eulerian Modeling Approach for the Prediction of Bi-Disperse Gas-Solid Fluidized Bed

Eulerian gas-solid fluidized bed simulations of industrial processes are usually performed with mesh sizes much larger than the smallest meso-scale structure size because of computational resource limitation. Thus, these effective simulations do not fully account for the particle segregation effect (cluster or bubbles formation) and the lack in prediction of the meso-scale structures generally causes poor prediction of bed hydrodynamic [1]. According to previous studies, this effect seems to be very effective in bi-solid mixture with large inertia difference between the solid species.

Following Igci et al. [2], filtered approach may be developed where the unknown terms accounting for the influence of unresolved structures, called sub-grid contributions, have to be modelled in terms of the computed (filtered) variables. In the work presented here, the development of such modelling approach is based on a priori analysis of 3D periodic circulating bi-disperse gas-solid fluidized bed simulations using computational grids cell size of a few particle diameters to obtain mesh-independent results. Using the 3D N-Euler multiphase code NEPTUNE_CFD, separate transport equations are computed for the number density, velocity and random kinetic energy of the two solid species, coupled by collisions terms developed in the frame of kinetic theory of granular media supplemented by interstitial gas effect. These mesh-independent results are filtered using volume average to support the development of closure models for the subgrid fluid-particle and particle-particle interactions terms in bi-disperse gas-solid fluidized bed. These closure models are implemented in the multiphase code NEPTUNE_CFD and tested by performing coarse grid simulation of the periodic circulating bi-disperse gas-solid fluidized bed.

[1] Agrawal, K., Loezos, P., Syamlal, M., Sundaresan, S., 2001. The role of meso-scale structures in rapid gasâ??solid flows. J. Fluid Mech. 445, 151â??185.

[2] Igci Y., Adrews AT., Sundaresan S., Pannala S., Oâ??Brien T., Filtered two-fluid models for fluidized gas-particle suspensions, AIChE J., 2008;54:1431-1448.