The dynamics of settling particles in vertical channel flows: gravity, lift and particle clusters

The dynamics of dense finite-size particles in vertical channel flows Newtonian and viscoelastic carrier fluids are examined using particle resolved simulations. Comparison to neutrally buoyant the same configuration highlights effect settling. volume fraction is $5\%$, a gravity field acts counter flow direction. Despite modest density ratio ($\rho_r = 1.15$), qualitative changes arise due relative velocity between fluid phases. While homogeneously distributed core channel, mean concentration profile peaks near-wall region competition shear- rotation-induced lift forces. These forces act cross-stream directions, analyzed by evaluating conditional averages along individual trajectories. correlation angular translational velocities significance Magnus force both spanwise wall-normal directions. collective behaviour also intriguing. Using \Voro analysis, strong clustering identified near wall, which shown alter their streamwise velocities. This attributed preferential transport aggregated towards wall. practical implication non-uniformity distribution significant increase drag. When viscoelastic, migration enhanced leads larger stresses, thus negating capacity viscoelasticity reduce turbulent