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Our research is concentrated in the area of fluid-particle and granular flows/processes. The research is focused on developing a fundamental understanding of the hydrodynamics and heat and mass transfer in these systems and applying this understanding to improve the design and operation of chemical and pharmaceutical processes. Fluid-particle and granular flows exhibit rather complex
behavior, for example, the occurrence of bubbles and clusters in gas-particle
flows, and clogging and size segregation in granular flows. We study the
mechanics of these systems through combined numerical, theoretical and
experimental efforts. Particle/molecular dynamic simulations and experiments
on model systems are carried out to explore the physical mechanisms governing
the flows. High performance computing is used together with modeling
to obtain specific predictions on flows of practical interest. Applied
mathematics plays an important role in our research and recent advances
in bifurcation analysis and nonlinear dynamics allow us to systematically
examine stability and multiplicity of solutions. The following are some
examples of topics currently under investigation.
Gas-Particle and Gas-Liquid-Particle Flows
The goal of this research project is to develop an understanding
of gas-particle and gas-liquid-particle flows and apply equations of motion that can quantitatively
model such flows to acceptable engineering accuracy. At the present
units such as fluidized beds, slurry-bubble columns, risers and standpipes are designed
using correlations and empiricism, and costly pilot plants must
be built for each and every process. A reliable engineering model
describing the flow of suspensions of particulate material would
change this. The flows in such beds can be complicated,
with concentration waves moving through the bed. The occurrence
of these waves can have an adverse effect on the fluid-particle
mixing, and leads to problems with the scale-up of the beds. Our
research program is directed at determining the effect of such flows
on chemical reactors, and the modelling and scale-up of reactors.
Our efforts are aimed at matching computational results with experimental
results.
Flow and Segregation of Granular Materials
Industries that process particulate materials are plagued by poor performance
due to unwanted segregation, and erratic flow rates caused by complex rheological behavior. The
goal of this research is to understand the relationship between the collective
motion of the particles and the particle properties, boundary conditions
and the history of the system. Our research involves experimental and
numerical studies of granular materials in systems such as shearflows, chutes, hoppers and vibrated beds. We are particularly interested in (1)
the mechanisms leading to microstructure and segregation in such flows,
and (2) gaining an understanding of issues affecting scale-up. We are
exploring hybrid continuum-microscopic simulations of particulate materials
where macroscopic flow equations are solved simultaneously with molecular/particle
dynamic simulations.
Research on granular flows includes characterization of a granular shear instability, which can be observed at the interface between two streams of grains downstream of a splitter plate. In fluids research, a geometry used to probe the responses of liquids and gases to shear, is flow downstream of a splitter plate. This flow can exhibit the Kelvin-Helmholtz instability, leading to transitions between steady, oscillatory, and turbulent states that have been productively investigated for over a century. We have observed behaviors for grains that are in many ways as rich and enlightening as those for fluids.
Work on chutes has led to the observation of chevron-shaped surface waves localized to the near wall region.
Experimental measurements and Particle Image Velocimetry (PIV) analysis indicates that subsurface circulation driven by velocity gradients near frictional walls plays a central role in the pattern formation mechanism, suggesting that the wave generation is controlled by the granular analog of a fluid boundary layer.
Nonlinear Dynamics of Transport Processes in Fluid-Particle Systems
Research in this area includes fluidized bed adsorption, drying of supported catalysts and agitated drying of pharmaceutical crystals.
Drying of Supported Catalysts: In catalyst manufacture, drying can affect the final distribution of the active component on the support. Unless this process is carefully controlled, useless batches may be produced that must be discarded because of low catalytic activity.
A modeling and experimental effort has been developed in order to study the impact of drying conditions and system properties on the final catalyst profile in supported impregnation catalysts
Agitated Drying of Pharmaceutical Crystals: The main goal of this work is to develop a fundamental understanding on how a wet granular material behaves during drying with shear. Shear can lead to crystal size reduction by attrition and crystal size enlargement by agglomeration. The attrition and agglomeration effects can be undesirable in real systems and can create non-uniform drying conditions.
Fluidized Bed Adsorption: Primary recovery and purification continues to be a significant limiting factor in the overall economics of therapeutic protein production. Fluidized bed adsorption or expanded bed adsorption can perform product capture, feedstock clarification and product concentration in one unit operation. Making use of a combination of experiments and modeling, we are developing a quantitative framework for separating the contributions of mass transfer, hydrodynamics and adsorption.
Dr. Benjamin J.
Glasser's Website
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Selected Publications
Conway, S.L., and Glasser, B.J., Density Waves and Coherent Structures in Granular Couette Flows, Phys. Fluids, 16, 509-529, (2004).
Lekhal, A., Glasser, B.J., and Khinast J.G., Influence of Ph and Ionic Strength on the Metal Profile of Impregnation Catalysts, Chem. Eng. Sci., 59, 1063-1077, (2004 ).
Liss, E., Conway, S.L., Zega, J.A., and Glasser, B.J., Segregation of Powders during Gravity Flow through Vertical Pipes, Pharm. Tech., 28:2, 78-96, (2004).
Lekhal, A., Girard, K. P., Brown, M. A., Kiang, S., Glasser, B.J., and Khinast J., Impact Of Agitated Drying On Crystal Morphology: KCL-Water System, Powder Technology, 132, 119-130, (2003).
Raffensberger, J., Koynov, A.A., Glasser, B.J. and Khinast, J.G. Influence of Particle Properties on the Yield and Selectivity of Fast Heterogeneously Catalyzed Gas-Liquid Reactions, Int. J. Chemical Reactor Eng., 1, A15, 1-16, (2003).
Conway, S.L., Goldfarb, D.J., Shinbrot, T., and Glasser, B.J., Free Surface Instabilities in Rapid Granular Chute Flows, Phys. Rev. Lett., 90, 074301, 1-4, (2003).
Liss, E., Conway, S.L. and Glasser, B.J., Density Waves in Gravity-Driven Granular Flows, Phys. Fluids, 14, 3309-3326 (2002).
Johri, J., and Glasser, B.J., Connections between Density Waves in Fluidized Beds and Compressible Flows, AIChE J., 48, 1645-1664, (2002).
Muzzio, F.J., Shinbrot, T. and Glasser B.J., Powder Technology in the Pharmaceutical Industry: The Need to Catch Up Fast, Powder Tech., 124, 1-7, (2002).
Goldfarb, D., Glasser, B.J., and Shinbrot, T., Shear Instabilities in Granular Flows, Nature, 415, 302-305, (2002).
Publication List
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