Numerical simulations of positively-buoyant suspension in a horizontally rotating cylinder were performed to study the formation of radial and axial patterns. The order parameter for lowfrequency segregated phase and dispersed phase is similar to that predicted for the settling suspension by J. Lee, and A. J. C. Ladd [J. Fluid Mech., 577, 2007], which is the average angular velocity of the particles. The particle density profiles for axial bands in the buoyancy dominated phase shows an amplitude equivalent to the diameter of the cylinder. Axial density profiles show sinusoidal behaviour for drag dominant phase and oscillating sinusoidal behaviour for centrifugal force dominant phase. Results also indicate that the traveling bands are formed as a consequence of the inhomogeneous distribution of particles arising from a certain imbalance of drag, buoyancy and centrifugal forces. In the centrifugal limit, particles move towards the centre of the cylinder aggregating to form a dense core of particles with its axis coinciding with that of the rotating cylinder, a behaviour which is in contrast to the sedimenting particles. The particle distribution patterns obtained from the simulations are found to be in good agreement with the experiments of Kalyankar et al. [Phys. Fluids, 20, 2008].

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<p>Intense sediment transport situations such as debris flows and mudslides consisting of fine-grained particles can pose serious threats to human infrastructures and lives. A thorough understanding of the rheology of such cohesive granular flows is crucial to predict the behavior of these types of flow and to mitigate their damaging effects. Whereas the rheology of non-cohesive granular flows has been studied extensively in the literature, the effect of cohesive inter-particle forces on the rheological behavior is still obscure and has not been sufficiently addressed. In this study, employing particle-resolved Direct Numerical Simulations, we simulate non-cohesive and cohesive dense suspensions sheared by moving walls. We perform several high-resolution simulations and compare the rheological parameters of the suspensions for different values of a dimensionless cohesive number, <em>Co</em>. Direct Numerical Simulations enable us to delve into the stress profiles in the vertical and streamwise directions and explore the contribution of different particle and fluid stresses to the total stress in each direction. We will also investigate the microstructure of the suspension and relate the microscopic interactions to macromechanical, rheological behavior of the dense cohesive suspension. </p>