A hybrid continuum/PDF model for the prediction of dispersed particulate flow

• Published in: International journal of multiphase flow Vol. 39; pp. 148 - 158
• Main Authors: Lad, Bharat, Issa, Raad I.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2012; Elsevier
• Subjects: Algebraic stress model; Continuums; Dispersed flow; Dispersion; Exact sciences and technology; Fluid dynamics; Fluxes; Fundamental areas of phenomenology (including applications); Jets; Kinetic model; Mathematical models; Multiphase and particle-laden flows; Nonhomogeneous flows; Physics; Portable document format; Transport equations; Turbulent flows, convection, and heat transfer; Two-fluid model; Walls; Kinetic model; Dispersed flow; Algebraic stress model; Two-fluid model; Dispersed phase; Circular jet; Digital simulation; Two fluid model; Velocity distribution; Particle suspension; Confined jet; Two-phase flow; Hybrid model; Modelling
• ISSN: 0301-9322; 1879-3533
• DOI: 10.1016/j.ijmultiphaseflow.2011.10.002

► We propose a CFD model for confined dispersed two-phase flows that is industrially cost effective. ► We employ a traditional two-fluid algorithm with particulate equations derived from the KM PDF. ► Particulate stresses are closed using an algebraic stress model, derived from the kinetic PDF model. ► A wall flux database is used at the wall, constructed by the pre-integration of the kinetic PDF model. ► A free jet and confined jet flow is modelled and shows promising results. The paper presents a hybrid continuum-PDF model for the prediction of dispersed two-phase (solid/gas) flows within confined geometries. Based upon the framework of the two-fluid model, the dispersed phase continuum transport equations are replaced by similar ones derived from the Kinetic Model (KM) PDF transport equations. Closures for the kinetic stresses of the dispersed phase comprise an algebraic stress model (ASM) and a transport equation for the turbulent kinetic energy ( k d ) – both of which have also been derived from the KM PDF transport equation. The dispersed phase wall boundary conditions are implemented in the same manner as the “wall functions” approach for the numerical solution of the carrier phase continuum equations; however the wall fluxes are calculated from the direct solution of the KM PDF – which has been pre-integrated for a range of bulk flow conditions to produce a database for wall fluxes that are used to set appropriate values at every point along the walls. Validation is made by comparisons against experimental data for a round jet and a confined planar jet. The predictions are in good overall agreement with measurements in both cases. The proposed ASM- k d model shows particularly promising results for the jet flow case, with a large improvement on the results of the standard two-fluid models. However, the planar jet case showed that due to the perfectly reflecting wall condition assumptions used in the production of the wall fluxes database, the particulate mean axial velocity is under-predicted.