Particle motion characteristics and structural properties of impingement plane in dense granular opposed impinging jets

The macro motion characteristics of particles and multi-scale structure characteristics of impingement plane in dense granular opposed impinging jets are numerically studied by Discrete Element Method (DEM), and a wave-structure extraction method based on Galilean-decomposition was proposed for quantitative analysis of the impact surface structure. The nozzle spacing is 20 mm, and the particle velocity at the nozzle outlet is 10 m/s. Five particle solid contents (0.05–0.4) and four nozzle diameter (2-8 mm) were tested. The results indicate that both the solid content and nozzle diameter promote the development of the “dead zone” structure at the center of the impact zone, ultimately resulting in the formation of a film-like impingement plane. As the solid content increases, the “dead zone” structure initially expands and then diminishes, while particle-concentrated regions emerge on both axial sides of the impact zone, and the particle concentration distribution along the axial jet centerline evolves from a single peak to a double peak. The wavy structure of the granular film impingement plane arises from the radial gradient of the axial jet transport velocity. Specifically, as the radius increases, the granular transport flow rate conveyed from the axial jet to the radial jet on the cross-section of the axial jet gradually increases. Therefore, the “dense-sparse alternating” granular film wave structure is more significantly influenced by the nozzle diameter; meanwhile, the solid content has a more pronounced impact on the diameter of the circular stagnation zone, as well as the particle concentration within the particle enrichment regions of the wave structure. • Quantitative analysis of impact surface structure in dense granular impinging jets. • Interparticle collisions cause impingement plane evolve towards granular film. • Solid content or nozzle diameter promote the formation of granular film structures. • Non-uniform granular transport flow rate creates wave pattern on impingement plane.