(6dy) Experimental and Computational Studies of Fluid-Particle Flow Systems

Fluid-particle flow
systems, such as fluidized beds, exhibit a rich array of complex physical
phenomena and are vital to the pharmaceuticals, oil, chemicals and food
industries. While these systems have been used industrially for nearly a
century in processes ranging from fluidized catalytic cracking to granulation,
they are also important in new applications to solve 21^st Century
problems, such as chemical looping combustion for efficient carbon capture and
sequestration. Currently, the energy and economic efficiency of these systems,
as well as the use of these systems in new processes, is limited by a lack of
in-depth understanding of the complex physics occurring in these systems over a
wide range of length scales, and the relationship between this physics and
reaction kinetics. Recently, the application of new experimental techniques and
computational models has started to shed new light on these fascinating and
industrially important physical phenomena.

Over the course of my
research career, I have combined computational and experimental techniques to
provide understanding of the fundamental science of fluidized beds beyond that
which could be achieved using any individual technique. During my PhD at the
University of Cambridge, I created a 3-D cylindrical Euler-Lagrange model of
fluid-particle flow systems to simulate fluidized beds in their most commonly
used state. I compared simulation predictions with previously obtained
experimental results in order to validate the model, shed light on the nature
of certain experimental techniques and reveal the origin of pressure
oscillations in fluidized beds. Additionally, I developed new experimental
techniques in order to conduct the first ever measurements of gas velocity and
velocity distribution in a fluidized bed of particles using magnetic resonance
imaging (MRI). These measurements provide the first data and details showing
the distributions in gas velocities in different states of fluidization:
minimum, homogeneous, and bubbling fluidization. I compared these results with
classical analytical theory for gas flow in fluidized beds, in order to provide
insights on the validity of theories used every day by industrial
practitioners. As a post-doctoral researcher at Princeton University, I am
bridging my doctoral research by investigating how computational predictions of
gas phase dynamics match my experimental results. I am also branching out into
new areas of fluid-particle flow by developing computational models to
investigate wet fluidized beds, in which a small amount of liquid forms bridges
between particles, leading to agglomeration, as well as falling granular jets which
exhibit phenomena indicative of an effective surface tension.

As a research faculty
member, I plan to expand upon the foundation I have built in order to explore
the critical interplay between physics and chemistry in fluid-particle flow
systems over multiple length scales. My research program will involve developing
and combining multi-scale modeling and multi-scale measurement efforts to
provide insights on physical phenomena that occur on length scales varying from
one particle diameter to a reactor tens of meters in diameter. This research
path will also entail coupling the chemical reactions with the modeling and
measurement techniques in a way such that the relationship between the physical
and chemical phenomena can be better understood. Finally, my program will
involve direct collaboration with researchers and industrial practitioners who
build fluidized beds for applications such as combustion and catalysis, in
order to aid in the design and measurement of their experiments. My ultimate
aim is to enable the next generation of two-phase granular flow systems, which
can offer real world solutions to global challenges ranging from clean energy
production to food supply to safe and economic production of pharmaceuticals.

I also intend to use my
unique educational background, coming from a double major in physics and
chemical engineering as an undergraduate at MIT to a PhD student and Gates
Scholar at the University of Cambridge to a post-doctoral researcher at
Princeton University, to enhance chemical engineering education at a research
university. From my experiences, I have seen a number of ways in which the
on-campus undergraduate and graduate education experience in the U.S. can be
further enhanced. Firstly, as a supervisor in the education system unique to
Oxford and Cambridge, I have seen the benefits of students discussing material and
problems in 2-to-4-person student groups with a graduate-level supervisor in an
organized yet open-ended discussion setting. Secondly, as a Gates Scholar, I
have had the privilege of interacting with leading graduate students in diverse
disciplines, ranging from international relations to public health to
engineering; this experience has shown the exceptional and expansive nature of
the graduate education that comes from discussing important research problems
that cut across academic disciplines. As a faculty member, I plan to take an
active role in education to ensure more chemical engineering students at my
university are provided with these valuable learning opportunities.