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Granular flow in a rotating tumbler is of theoretical and industrial significance. However, in spite of its relative simplicity, little is known about the dynamics of the top flowing layer. Here we present an experimental study of the velocity field within the fluidized layer of monodisperse particles in a quasi-2D ~two-dimensional! rotating tumbler in the… (More)

- Yeomin Yoon, Richard M. Lueptow
- Journal of membrane science
- 2005

Rejection characteristics of organic and inorganic compounds were examined for six reverse osmosis (RO) membranes and two nanofiltration (NF) membranes that are commercially available. A batch stirred-cell was employed to determine the membrane flux and the solute rejection for solutions at various concentrations and different pH conditions. The results… (More)

- Yuan Yao, Gonghu Li, Shannon Ciston, Richard M. Lueptow, Kimberly A. Gray
- Environmental science & technology
- 2008

Electron-hole recombination limits the efficiency of TiO2 photocatalysis. We have investigated the efficacy with which anatase/carbon nanotube (CNT) composite materials reduce charge recombination and enhance reactivity. We synthesized nanostructured assemblies composed of different proportions of anatase (5 or 100 nm) and either single-or multi-walled… (More)

The stability of supercritical Couette flow has been studied extensively, but few measurements of the velocity field of flow have been made. Particle image velocimetry (PIV) was used to measure the axial and radial velocities in a meridional plane for non-wavy and wavy Taylor–Couette flow in the annulus between a rotating inner cylinder and a fixed outer… (More)

- Yefim Dain, Richard M. Lueptow
- The Journal of the Acoustical Society of America
- 2001

Vibrational relaxation accounts for absorption and dispersion of acoustic waves in gases that can be significantly greater than the classical absorption mechanisms related to shear viscosity and heat conduction. This vibrational relaxation results from retarded energy exchange between translational and intramolecular vibrational degrees of freedom.… (More)

Acoustic attenuation in a mixture of gases results from the combined effects of molecular relaxation and the classical mechanisms of viscosity and heat conduction. Consequently, the attenuation depends on the composition of the gas mixture, acoustic frequency, temperature, and pressure. A model of the relaxational attenuation that permits the calculation of… (More)

A dominant aspect of granular flows is flow in thin surface layers. While an understanding of the dynamics of dry granular surface flow has begun to emerge, the case of flow when air is completely replaced by a liquid is largely unexplored. Experiments were performed using particle tracking velocimetry (PTV) in a quasitwo-dimensional rotating tumbler to… (More)

- Antje Brucks, Tim Arndt, Julio M. Ottino, Richard M. Lueptow
- Physical review. E, Statistical, nonlinear, and…
- 2007

We consider the impact of the effective gravitational acceleration g{eff} on gravity-driven granular shear flow utilizing a tumbler of radius R rotating at angular velocity omega when g{eff} is varied up to 25 times the gravitational level on Earth in a large centrifuge. The Froude number Fr=omega{2}R/g{eff} is shown to be the proper scaling to characterize… (More)

- Yi yfan Fan, Youcef Boukerkour, Thibault Blanc, Paul Umbanhowar, Julio M. Ottino, Richard M. Lueptow
- Physical review. E, Statistical, nonlinear, and…
- 2012

Segregation and mixing of granular mixtures during heap formation has important consequences in industry and agriculture. This research investigates three different final particle configurations of bidisperse granular mixtures--stratified, segregated and mixed--during filling of quasi-two-dimensional silos. We consider a large number and wide range of… (More)

- Florent Pignatel, Caroline Asselin, Lucas Krieger, Ivan C. Christov, Julio M. Ottino, Richard M. Lueptow
- Physical review. E, Statistical, nonlinear, and…
- 2012

The scaling properties of the continuous flowing layer in a quasi-2D circular tumbler half filled with a granular material are studied experimentally in the presence of three different interstitial fluids (air, water, and glycerine). In the dry case, the dimensionless flowing layer thickness δ(0)/d scales with the dimensionless flow rate Q(dry)(*) =… (More)