Density-driven submerged granular flows in rotating drums

Granular flows and segregation phenomena play critical roles in diverse natural and industrial processes. We investigated the dynamics of mono-dispersed and binary granular mixtures in submerged rotating drums using combined experimental and numerical methods. Mono-dispersed granular flows demonstrate clear transitions between rolling and cascading regimes, strongly influenced by particle density, fluid properties, and rotation speeds; these transitions are effectively captured by a modified Froude number (Fr*) incorporating particle-fluid density differences. Extending this analysis to binary mixtures reveals a density-driven segregation mechanism, with the mixing index exhibiting an exponential relationship with the effective density ratio (D). Our findings offer enhanced fundamental understanding of submerged granular flows and segregation dynamics, providing valuable insights for both scientific exploration and engineering practices.