Hydrodynamics of Confined Free-Falling Polyhedral Particles in Quiescent Fluids Under Varying Thermal Conditions

In this work, the settling of polyhedrons is studied in confined cylindrical columns, applicable to applications in sedimentation tanks and separators. This paper reports 63 experiments done in a glass cylinder with a diameter of 80 mm at confinement ratio (λ = de/D = 0.31), which represents a case of high confinement needing corrections to the drag coefficient depending on the Reynolds number. Four shapes have been considered; cube (φ = 0.806), cuboid (φ = 0.690), tetrahedron (φ = 0.671), and spheres (φ = 1.000), used for testing purposes, fabricated using Epoxy-Resin Clay and Aluminum alloy having equal volumes (de = 24.8 mm). Key findings are: (i) wall corrected CD-Re-f standards up to Re = 2.5 × 104; (ii) proof of the wall correction approach using spheres with deviations of 4.16% for the Clift-Gauvin data and 7.08% for Schiller-Naumann; (iii) confirmation of the transition from the Stokes to the transitional regime for glycerol at Re increasing by 66% when temperature rose from 30 to 50 °C; and (iv) a new correlation of drag force, CD(Re, φ, λ), developed for confined conditions, which is applicable within the range ±6.4%, 0 = ≤ = 0.40 and 0.671 = φ = 1.000.