Experimental and numerical study of settling of dual cubes released side-by-side

In this study, the settling behaviour of two cubes and two spheres released side-by-side in a quiescent fluid is investigated through both experimental and numerical simulation approaches. Particle Tracking Velocimetry (PTV) and Particle Image Velocimetry (PIV) are employed to capture particle trajectories, settling velocities, and the surrounding flow fields. Concurrently, coupled Smoothed Particle Hydrodynamics–Distributed Contact Discrete Element Method (SPH-DCDEM) simulation is performed to reveal detailed three-dimensional flow structures and pressure distributions. The results indicate that the initial particle spacing significantly affects the settling dynamics by altering the flow patterns between the two particles and influencing their rotational motion. In extreme cases, it even modifies the overall particle trajectories from the typical three-stage process to a four-stage process. Moreover, the cubic shape induces flatter streamlines, stronger recirculation zones and wake structures, and a distinct region of horizontal reverse flow. Regions of high vorticity and high pressure are alternately distributed along the edges and faces of the cubes. A strong coupling is found between the flow field structure and the particle’s motion, and the evolution of particle trajectories is elucidated by analysing the development of pressure distribution over the entire settling process. By decoupling the multiple effects driving free settling dynamics, the repulsion mechanisms are clarified and the force magnitudes quantified. These findings deepen our understanding of the settling behaviour of non-spherical particles and offer valuable insights for predicting particle dynamics in environmental and industrial applications.