Simulations of scalar dispersion in fluidized solid–liquid suspensions



Direct, particle-resolved simulations of solid–liquid fluidization with the aim of quantifying dispersion have been performed. In addition to simulating the multiphase flow dynamics (that is dealt with by a lattice-Boltzmann method coupled to an event-driven hard-sphere algorithm), a transport equation of a passive scalar in the liquid phase has been solved by means of a finite-volume approach. The spreading of the scalar—as a consequence of the motion of the fluidized, monosized spherical particles that agitate the liquid—is quantified through dispersion coefficients. Particle self-diffusivities have also been determined. Solids volume fractions were in the range 0.2–0.5, whereas single-sphere settling Reynolds numbers varied between approximately 3 and 20. The dispersion processes are highly anisotropic with lateral spreading much slower (by one order of magnitude) than vertical spreading. Scalar dispersion coefficients are of the same order of magnitude as particle self-diffusivities. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1880–1890, 2014