Particulate flow analysis in inclined pipes and transfer chutes using tomography imaging,discrete element simulations and continuum modeling approaches

In particulate material transfer systems,traditional shear test based steady state analysis can provide some insight into the strength of the bulk material and subsequent resistive frictional forces during flow.For fast flowing transfer points,dynamic flow conditions dominate and additional modelling techniques are required to improve design guidance.The research presented shows the evolution of a design solution which utilises two distinct processes;a continuum method and a discrete element method(DEM). Initially,the internal structure of dense granular flow,down vertical and inclined pipes was investigated using a twin sensor,12 electrode electrical capacitance tomography device.Subsequently,DEM simulations were conducted using the commercial software,PFC3D.Initially,two particle types and their flow behaviours were analysed:plastic pellets and sand.The pipe angle was varied between 0°and 45°to the vertical.For both the plastic pellets and the sand,good qualitative agreement was found with the spatial particle concentration analysis.Generally,the flow had a dense particle region at its core with the particle concentration reducing away from this core.As expected,at 0°, the core was centrally located within the pipe for both the plastic pellets and sand.At pipe angles 5°or greater,the dense core of particles was located on or near the pipe wall.Average flow velocity analysis was also conducted using the results of wall friction test analysis.The velocity comparisons also showed good agreement between the ECT image analysis and the DEM simulations. Subsequently,the DEM method was used to analyse a complex transfer system(or chute) with the continuum method providing comparative flow analysis with the DEM flow analysis.

Particle shape characterisation and its application to discrete element modelling

Increasing importance has been placed on particle shape implementation within discrete element mod elling （DEM） in order to more accurately reflect the nonspherical behaviour of the bulk material being handled. As computational resources grow, complex particle shapes are increasingly being modelled as the associated simulation times become more realistic to provide timely solutions. The objective of this research is to assess particle shape descriptors through a digital image segmentation technique, and to further implement particle shape parameters into generation of corresponding irregular shaped DEM particles. Separated and lumped particle images were analysed and reconstructed through the devel opment of two distinct methodologies. Subsequently, various particle shape descriptors were obtained using combinations of image segmentation algorithms, including mathematical morphology processing, thresholding, edge detection, region growing, region splitting and region merging. DEM particles were subsequently created using particle shape results obtained above. Shape parameters of DEM particles were then examined and validated against the real particle shape parameters.