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Tapered gas-solid risers have been used in some industrial processes in order to adapt to the requirements of various reactions, but little attention was paid to these reactors in previous investigation. In this work, three-dimensional gas-solid flow in tapered-out and tapered-in risers was simulated by the two-fluid model using an improved structure-dependent drag based on the EMMS model. The EMMS model was solved at different axial levels to determine different correlations of heterogeneity index with voidage, which were then interpolated between these levels to improve the prediction of varying interphase drag in the tapered risers. Considering the axial variation of the EMMS drag, the simulation predicts much more reasonable flow dynamics in the tapered risers than those coupled with an average EMMS drag or homogeneous drag laws. The axial and radial heterogeneities as well as the parametric effects on the flow dynamics in the tapered risers were discussed in detail, so as to provide reference for the proper design of tapered gas-solid riser reactors. Unlabelled Image • Tapered gas-solid risers are studied by three-dimensional numerical simulation. • An improved EMMS drag is calculated and incorporated into the simulation. • Axial variation of drag is determined by interpolating between various heights. • EMMS-based simulation predicts reasonable flow dynamics in the tapered risers. • Parametric effects on flow dynamics in the tapered risers are discussed in detail. [ABSTRACT FROM AUTHOR]

This work presents a computational model for a discontinuous fibre composite manufacturing process. The alignment mechanism of this novel process, called the High Performance Discontinuous Fibre (HiPerDiF) method, involves highly coupled fluid-structure interactions. Fibres with a length on the order of a few millimetres are placed in a water suspension, sprayed between two parallel plates and deposited on a moving belt to make an aligned discontinuous fibre tape. This technology can be used as part of a composites recycling process to remanufacture reclaimed fibres into valuable recycled composite feedstock by ensuring a high level of alignment. In order to industrialise this process, the throughput must be increased whilst maintaining the high level of alignment. This work aims to assist this development by modelling the alignment mechanism using smoothed particle hydrodynamics (SPH). It is shown through comparison to experiments that SPH models the process well and captures the influences affecting fibre alignment. [ABSTRACT FROM AUTHOR]