Particle segregation and diffusion in fluid-saturated granular shear flows

Using coupled granular-fluid simulations we study the particle size segregation and diffusion in sheared granular flows immersed in different ambient fluids. Both segregation and diffusion decrease with the fluid viscosity but only after exceeding a certain threshold value. Decreasing the relative density between the particles and the fluid further slows down segregation but does not significantly affect diffusion. Empirical relationships for the segregation velocity and diffusion coefficient are developed in terms of the Stokes number which are used to model the segregation-diffusion process across different types of fluids.