Professor Paul Dimotakis

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Professor Paul Dimotakis John K. Northrop
Professor of Aeronautics and Professor of
Applied Physics Research Topics
GALCIT

• Turbulent mixing and chemical reactions in
  subsonic and supersonic free-shear flows
• Hydrocarbon flames under variable-pressure
  conditions
• Rayleigh-Taylor-Instability flows
• Mixing and the geometry of surfaces and
  interfaces in turbulence
• Scalar dispersion in turbulent boundary layers
• Aerooptical effects in turbulent free-shear
  flows
• Image Correlation Velocimetry

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Professor Paul Dimotakis Current Research
Interests
Turbulent mixing and chemical reactions in
subsonic and supersonic free-shear flows Faculty
P. Dimotakis Staff G. Katzenstein, D.Lang
This, primarily, experimental work in
chemically-reacting and nonreacting flows, is
conducted in the GALCIT supersonic shear layer
(S3L) combustion facility, where high-speed
freestream Mach numbers in the range 1.1 lt M1 lt
3.2 and low-speed freestream Mach numbers in the
range 0.3 lt M2 lt 1.3 can be attained. The
investigations focus on turbulence-generated
unsteady-wave phenomena, turbulent large-scale
behavior, as well as Reynolds number and Mach
number effects on turbulent mixing, under
compressible and incompressible flow conditions.
The experiments are conducted in a
near-atmospheric-pressure environment, at high
Reynolds number, permitting the fast chemical
kinetics of such reactants as hydrogen and
fluorine to be used to infer the extent of
molecular mixing under high-speed
(subsonic/supersonic) flow conditions. Such high
test-section pressures also allow a host of laser
diagnostics, coupled with digital-imaging
techniques, to be utilized in probing and
documenting the various phenomena. The main
thrust, at present, is an extension to other,
more-complicated flow geometries, as occur in
SCRAMJET devices, focusing on both internal- and
external-flow configurations and various
mixing-enhancement and drag-reduction
schemes. Hydrocarbon flames under
variable-pressure conditions Faculty P.
Dimotakis, D Meiron, T. Mattner
Collaborators F.Egolfopoulos (USC) Staff G.
Katzenstein, D. Lang Students J. Bergthorson,
K. Sone, ? This is a combined experimental and
computer-simulation effort to explore the
dynamics of hydrocarbon flames under
variable-pressure and high strain-rate
conditions. This flow/combustion regime is
important in many contexts, including high-speed,
hydrocarbon-fueled propulsion applications. The
experiments, will investigate ignition, flame
speed, and extinction behavior of hydrocarbon
fuels in the C1-C4 range. Using tunable-laser
excitation and high-frame-rate digital imaging,
flame propagation, extinction, and profiles of
radical chemical species will be measured in
stagnation-flame flows, as a function of
pressure, and compared with full chemical-kinetic
simulations. The purpose of these studies is to
extend our understanding and experimental
database for these phenomena and compare results
with detailed predictions from several
chemical-kinetics models, permitting their
improvement. Rayleigh-Taylor-Instability
flows Faculty P. Dimotakis, D. Meiron
Post-docs T. Mattner Collaborators Andrew
Cook, Paul Miller (LLNL) Staff D. Lang, S.
Lombeyda (Caltech CACR) Students
? Rayleigh-Taylor instability occurs when
low-density fluid accelerates high-density fluid
equivalently, when high-density fluid finds
itself over low-density fluid in a gravitational
(accelerating) field. The dynamics of this flow
are crucial to our understanding of many
combustion phenomena, in astrophysical and
geophysical flows, in inertial-confinement
(laser) fusion, in accelerating variable-density
and two-phase flows, and many others. Work at
this time relies on large-scale Direct Numerical
Simulations (DNS).
GALCIT