Abstract
Large-scale gas-solid flow systems, e.g., fluidized beds, cyclone separators and pneumatic conveyors, are often encountered in chemical engineering. Numerical modeling technologies are widely applied for design and understanding of complex phenomena in these gas-solid flow systems, for which the coupled model of the discrete element method (DEM) and computational fluid dynamics is generally employed. However, application of the numerical simulations for these systems is still limited because the number of the particles that can be modeled (about several hundreds of thousand) is quite small comparing with the immeasurable number of particles used in the industrial processes, and not sufficient to fully understand the complex behavior in these processes. The coarse graining DEM is then developed to provide an alternative approach for modeling the real industrial processes. Accuracy of the coarse graining DEM has been proven for simple systems so far. In the present study, applicability of the coarse graining DEM for complex shaped domains is explored, for which typical industrial processes, such as fluidization with inserted tubes, and powder flow into a confined space, are considered. In these calculations, signed distance functions (SDF) and immersed boundary method (IBM) are used to model an arbitrary shape wall boundary in a gas-solid flow. Both numerical modeling using the coarse graining DEM and experimental investigation are performed with a thorough comparison between the experimental and numerical results. It is demonstrated that the coarse graining DEM is capable of accurately modeling of industrial gas-solid two-phase systems. Besides, this numerical approach is shown to provide valuable information such as pressure profile during powder injection and interaction between bubbles and structures in a fluidized bed.