https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/particlesize-and-density-segregation-in-granular-freesurface-flows/9D7F14256E5E714949326EB22D7448A9
Particle-size and -density segregation in granular free-surface flows - Volume 779
particle sizefree surfacedensitysegregationgranular