Parameter Study and Calibration of SPH–DEM Coupling Simulations for Fluid–Granular Solid Systems

The presence of fluid–granular solid flows can be found in a wide range of industrial applications such as pneumatic conveying, wet ball milling, and slurry transport. The majority of such fluid–granular solid flows are too intricate to be sufficiently modelled by fundamental theories. As a result, there has been a research effort conducted on using computer-aided engineering (CAE) tools to model industrial systems that handle fluid–granular solid flows. Apart from using conventional methods, some researchers have explored the coupling between smoothed particle hydrodynamics (SPH) and discrete element method (DEM) to model specific fluid–granular solid flows with free surfaces, complex geometries, mobile interfaces, large deformations, and fast dynamics. However, even though many feasibility studies have been conducted on SPH–DEM simulations, there is still a general lack of standardised methodologies to conduct parameter study and calibration of this newer simulation tool.

With this motivation, this thesis aims to develop a dedicated model parameter study and calibration framework for new SPH–DEM coupling models using bench-scale experiments. The developed framework is utilised to construct an SPH–DEM model to simulate the mixture between water and irregularly shaped cohesionless dark peach pebbles. In this framework, length scale refinement strategies are investigated to see if they can help a standard SPH implementation make accurate predictions of 3D free-surface fluid flows. Experimental test rigs are designed to accommodate for both a dry mode granular solid sample and a submerged mode fluid–granular solid mixture on the same system. Using the experimental data as the validation reference, a manual calibration process followed by a comprehensive calibration process are performed to obtain an understanding of how SPH length scales and DEM contact parameters affect the SPH–DEM simulation model.

While the research indicates a considerable challenge in using length scale refinement strategies to achieve simulation convergence only with a standard SPH implementation, it also illustrates that SPH length scale sizes, along with the DEM contact parameter values, have a substantial impact on the SPH–DEM results. The conducted manual and comprehensive calibration studies demonstrate the potential of a dedicated calibration framework to develop a fully calibrated SPH–DEM model. These studies also emphasise the need to treat dry mode DEM calibration and submerged mode SPH–DEM calibration independently.