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phone: (732) 445-6712



Jayati Johri

Doctoral Candidate


B.S., University of Texas at Austin, TX, 1996

Understanding gas-solid flows through modeling and experimental work on gas fluidized beds

My research is concerned with understanding the genesis and evolution of voidage waves in gas-fluidized beds. The occurrence of voidage or density waves such as bubbles, slugs and clusters in fluidized beds is an intriguing phenomenon that is still not completely understood. Fluidized bed reactors are widely used in industry and the occurrence of such waves can have a significant effect on the economics, safety and environmental impact of a reactor. Any practical design needs to account for this behavior, which is only possible with a thorough understanding of the phenomena of bubbling and slugging themselves.

A traditional approach to modeling gas-fluidized beds involves the formulation of a two phase continuum model which is used in conjunction with applicable closures. A very large number of terms come into play in these equations and even with the most detailed analysis, a fundamental understanding of the mechanics of bubbling and slugging is often not possible. In the theoretical component of my work, I have shown that under certain simplifying assumptions, the equations of motion and continuity for the gas and particles in a fluidized bed may be simplified to those of a fluid with variable density. By examining a simplified system, the minimum physics needed to capture the phenomenon of voidage waves in fluidized beds is determined.

The experimental component of my work is concerned with using a non-intrusive, vibrational probe to measure the granular temperature at the wall in gas-fluidized beds. Characterization of the state of the particles can be important for control of an industrial system and can also provide insight into the mechanics of gas-particle flows. In addition the fluctuating velocity of the particles impacts the solid phase stress which in turn has a large effect on the formation of bubbles, clusters and other density waves in such beds. In particular I have examined how the mean fluctuating velocity of the particles changes with gas flowrate, particle density and size. The main motivation behind this project is to relate the difference in the fluidization quality of various powders to their granular temperature profile.