People/Faculty/Glasser
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Benjamin J. GlasserProfessorB.S., University of the Witwatersrand, South Africa, 1989 Tel: (732) 445-4243 |
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The mechanics of fluidized beds, multiphase flows and reactors, flow and segregation of granular materials, nonlinear dynamics of transport processes in fluid-particle systems, Pharmaceutical Engineering.
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.
