An Explicit Method for the Packing Limit Management in Dense Gas-Solid Flow CFD Simulations on Both Structured and Unstructured Grids
International journal of Chemical Reactor Engineering
An explicit method for limiting the volume fraction of the dispersed phase in the CFD simulations of dense gas-solid flows is described and validated both on structured and unstructured computational grids. The procedure is based on the excess solids volume correction method proposed by Lettieri et al. (2003) , which has been extended in this work to non-uniform grids made of cells having different shape and size. The method has been implemented in OpenFOAM and validated through the simulation
... ugh the simulation of a fluidised bed in which the superficial gas velocity has been reduced to a value close to zero. KEYWORDS: multiphase CFD simulations, packing limit Brought to you by | Iowa State University Authenticated Download Date | 2/3/15 11:48 PM RESULTS The results of the two simulations discussed in §. 4 are reported in figure 3 , which shows the evolution in time of the particle phase volume fraction on the structured hexahedral grid (a) and on the unstructured tetrahedral grid (b). In both calculations, the solid particles continue to accumulate on the bottom of the bed, as a consequence of gravity, until the value of the solids volume fraction reaches its maximum, equal to the expected value for α s,max , which is never surpassed. The slight difference at the freeboard of the bed, which appears to be less sharp in (b), is a consequence of the adoption of the tetrahedral grid, which is less capable of capturing sharp interfaces than hexahedral discretisation. CONCLUSIONS The excess solids volume correction method proposed by Lettieri et al. (2003) , Cammarata et al. (2003) to enforce the particle phase packing limit in two-fluid simulations has been extended to unstructured grids.