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Particle-laden gas flows are common in many man-made and
natural environments. Their importance to industrial processes, agriculture,
and human health has made them of great theoretical and practical interest
over the past 50 years. Because the particles are carried by a turbulent gas
stream, progress in understanding and predicting behavior of particle-laden
flows has closely followed development in understanding and prediction of
turbulent flow. The motion of a particle in a gas flow is governed by the
particle inertia, gravity, and the particle’s interaction with the turbulent
fluid surrounding it. However, to determine the location and thus the local
turbulence surrounding the particle, the trajectory of the particle must be
known. It is this nonlinear coupling between the particle motion and the
turbulence that makes predicting particle dispersion in gas flow difficult.
Experimental and numerical studies of particle motion in simple flows, e.g.,
isotropic turbulence and uniform shear flow, have led to understanding of
the role played by particle inertia, particle mean drift velocity relative
to the gas flow, and the structure of the turbulence. The use of kinematic
simulations of turbulence and DNS has greatly augmented the experimental
findings. Predicting particle motion and dispersion in industrial or
environmental scale flows is challenging. Lagrangian simulation techniques
can typically only predict dispersion in one of the three directions,
usually one of the cross-stream directions. Two fluid models have potential
for predicting dispersion in all three directions. During the past two
decades, fundamental understanding of the dispersion of particles in simple
turbulent gas flows has been reached, and the capability of predictive tools
has increased exponentially as a result. This talk summarizes the current
state of knowledge about gas-particle flows, and highlights areas where more
research is needed.
Dr. David E. Stock is Professor of Mechanical Engineering
at Washington State University. Dr. Stock received his B.S. degree from Penn
State, M.S. from the University of Connecticut, and Ph.D. from Oregon State
University, all in Mechanical Engineering. He has performed research and
published extensively in a variety of areas, including experimental fluid
mechanics of free and confined flows, particle turbulence interaction in gas
flows, wind tunnel, field, and numerical studies of wind flow about
buildings and complex terrain, thermal and laser Doppler anemometry, and
prediction of electrostatic precipitator performance. His professional
activities have included service as Associate Editor of the Journal of
Fluids Engineering, member and Chair of the ASME Fluids Engineering
Division Executive Committee, and currently he is Chair, ASME/JSME Committee
for the 9th International Symposium on Gas-Solid Flows, June 2003. He is a
Fellow of ASME. |
