Adaptive resolution SPH method for non-Newtonian slurry mixing

The spiral rotating geometries, mechanical gaps, and free-surface flow in a twin-blade planetary mixer present major challenges to numerical models in terms of the simulation fidelity and efficiency. To research the stirring and kneading processes in this mixer, this paper proposed a smoothed particle hydrodynamics with adaptive spatial resolution (SPH-ASR) model for non-Newtonian fluids. An SPH coupling scheme between the non-Newtonian fluid and moving rigid bodies was developed, which combines dummy particles and a concentration function to handle arbitrarily shaped boundaries. In addition, the adaptive technique with a reference mass criterion achieved the adjustment of particle resolution in three-dimensional scenes, thereby overcoming the massive computational burden problem of mesh-free simulation for the industrial field. Two benchmark tests were used to demonstrate the model's accuracy, efficiency and robustness. The simulation results aligned well with the experimental data. Furthermore, in the actual twin-blade planetary mixer, the stress response and free-surface behaviors within kneading clearances were revealed. Engineering analysis indicates that the SPH-ASR model can serve as a promising tool to study the solid propellant slurry mixing and can be applied to different mixing devices.