Verification and Validation of Spatially Averaged Models for Fluidized Gas‐Particle Suspensions

Abstract

Two different methods for closure modeling of the unresolved terms appearing in the filtered two-fluid model are discussed and compared. The spatially averaged two-fluid model is based on generalizing the concepts of large eddy simulation to gas-particle flows. In the approximate deconvolution method-two-fluid model approach, the unresolved terms are modeled by an approximate deconvolution method, where an approximation of the unfiltered solution is obtained by repeated filtering. Finally, these models are applied to a lab-scale and a pilot-scale fluidized bed. Both approaches yield fairly good agreement with a highly resolved reference simulation as well as with experimental data. Additionally, both methods deliver reasonable grid-independent solutions up to a grid resolution of 2 cm in the case of Geldart type A particles.

Computational Fluid Dynamics Simulation of Iron Ore Reduction in Industrial‐Scale Fluidized Beds

“…with the correlation coefficient ξ f ϵ , the turbulent kinetic energy of the gas phase k f , and the variance of the void fraction ϕ 0 2 . A good approximation for the correlation coefficient is given by [53]…”

“…Finally, we used an average grid size of 2 cm, which is about 80 times coarser than the mesh resolution required to resolve all relevant heterogeneous structures. [53,55]…”

“…Thereby, we advanced a spatially averaged two-fluid model (SA-TFM), which is based on the concepts of turbulence modeling. [51][52][53][54][55][56][57][58] This approach appears to be more general than the functional fitting approach used in the literature. [53] In this article, we present a parcel-based Euler-Lagrange approach (aka DDPM), which accounts for the unresolved heterogeneous gas-solid structures by using subgrid models derived in our previous work.…”

“…[51][52][53][54][55][56][57][58] This approach appears to be more general than the functional fitting approach used in the literature. [53] In this article, we present a parcel-based Euler-Lagrange approach (aka DDPM), which accounts for the unresolved heterogeneous gas-solid structures by using subgrid models derived in our previous work. [51][52][53][54][55][56] Furthermore, this approach is verified in the case of a pilot-scale bubbling fluidized bed and the impact of subgrid structures is discussed.…”

“…[53] In this article, we present a parcel-based Euler-Lagrange approach (aka DDPM), which accounts for the unresolved heterogeneous gas-solid structures by using subgrid models derived in our previous work. [51][52][53][54][55][56] Furthermore, this approach is verified in the case of a pilot-scale bubbling fluidized bed and the impact of subgrid structures is discussed. Subsequently, we combine the present DDPM approach with a particle-based model for the direct reduction of iron ores, which has been proposed in our previous work.…”