68 citations · 187 across the 10 of their papers we have counts for
11 papers
Mechanisms leading to axial segregation of bidisperse particles in rotating tumblers
Umberto d'Ortona, Richard Lueptow, Nathalie Thomas
The origin of segregated axial bands for size-bidisperse particles in long rotating tumblers is a long-standing question in granular flows and a problem of both fundamental and pra…
Fluid transport by a single active filament in a three-dimensional two-phase flow
Qian Mao, Umberto d'Ortona, Julien Favier
Micro-scale cilia play a vital role in mucociliary clearance (MCC) in the human respiratory airways. In this numerical study, we examine fluid transport driven by the active beatin…
Origin of granular axial segregation bands in a rotating tumbler: An interface-mixing driven Rayleigh-Taylor instability
Umberto d'Ortona, Richard Lueptow, Nathalie Thomas
The origin of large and small particle axial bands in long rotating tumblers is a long-standing question. Using DEM simulations, we show that this axial segregation is due to a Ray…
Hydrodynamic coupling of a cilia--mucus system in Herschel--Bulkley flows
Q. Mao, Umberto d'Ortona, J. Favier
The yield stress and shear thinning properties of mucus are identified as critical for ciliary coordination and mucus transport in human airways. We use here numerical simulations…
Mechanisms for recirculation cells in granular flows in rotating cylindrical rough tumblers
Umberto d'Ortona, Nathalie Thomas, Richard Lueptow
Friction at the endwalls of partially-filled horizontal rotating tumblers induces curvature and axial drift of particle trajectories in the surface flowing layer. Here we describe…
Self-Induced Rayleigh-Taylor Instability in Segregating Dry Granular Flows
Umberto d'Ortona, Nathalie Thomas
Dry granular material flowing on rough inclines can experience a self-induced Rayleigh-Taylor (RT) instability followed by the spontaneous emergence of convection cells. For this t…
Evidence of reverse and intermediate size segregation in dry granular flows down a rough incline
Nathalie Thomas, Umberto D'ortona
In a dry granular flow, size segregation behave differently for a mixture containing a few large beads with a size ratio (S) above 5 (Thomas, Phys.Rev.E 62,96(2000)). For moderate…
Influence of Rough and Smooth Walls on Macroscale Granular Segregation Patterns
Umberto D'Ortona, Nathalie Thomas, Richard M. Lueptow
Size bidisperse granular materials in a spherical tumbler segregate into two different patterns of three bands with either small particles at the equator and large particles at the…
Influence of Rough and Smooth Walls on Macroscale Flows in Tumblers
Umberto D'Ortona, Nathalie Thomas, Zafir Zaman +1
Walls in discrete element method simulations of granular flows are sometimes modeled as a closely packed monolayer of fixed particles, resulting in a rough wall rather than a geome…
Slow axial drift in three-dimensional granular tumbler flow
Zafir Zaman, Umberto D'Ortona, Paul B. Umbanhowar +2
Models of monodisperse particle flow in partially filled three-dimensional tumblers often assume that flow along the axis of rotation is negligible. We test this assumption, for sp…
Granular Flows in a Rotating Drum: the Scaling Law between Velocity and Thickness of the Flow
Gwenaëlle Félix, Véronique Falk, Umberto D'Ortona
The flow of dry granular material in a half-filled rotating drum is studied. The thickness of the flowing zone is measured for several rotation speeds, drum sizes and beads sizes (…