Capability assessment of coarse-grid simulation of gas-particle riser flow using sub-grid drag closures

Our prior work developed an effective material-property-dependent sub-grid model (SGM) for efficient coarse-grid riser flow simulations. To apply this SGM for the purpose of designing and scaling-up riser reactors reliably, quantitative assessment in its predictive capability is required. Here, we quantify the influence of various model parameters with respect to time-averaging, grid resolution, time step, discretization scheme for convection terms, and solid-wall slip condition by implementing extensive three-dimensional coarse-grid simulations. Moreover, we compare several crucial SGM-based coarse-grid and coarse-grained methods to reveal their advantages and disadvantages. Detailed parametric sensitivity analyses demonstrate that the accurate determination of SGM appears to play a dominant role in successfully predicting hydrodynamics. The optimal selection of the other model parameters is suggested to realize a compromise between computation speed and accuracy. Overall, this fundamental study helps to quantitatively understand the predictability of SGMs for coarse-grid simulations of large-scale riser reactors. (C) 2019 Elsevier Ltd. All rights reserved.