so
the nasa lewis research center is in a
unique position
to take advantage of computational fluid
dynamics
structural mechanics and material
science
to develop new techniques for
multi-component
multi-discipline analysis design
and optimization of advanced engine
systems
to that end many of the lewis
organizations have formed research teams
whose activities are directed towards a
common long-range vision
of a numerical test cell for studies on
advanced
engine systems this unique computational
capability
in turn sets the stage for new levels of
understanding once the scientist or
engineer is satisfied
that the critical physics are being
modeled in the analysis
however confidence in computational
science
can only be achieved by detailed
comparison
with experimental data obtained in test
cells
or wind tunnels one such validation
experiment was performed in the 10 by 10
foot
supersonic wind tunnel at the nasa lewis
research center
in cleveland ohio in this experiment
instrumentation was installed in a
supersonic inlet
designed for mach 5 to provide detailed
data
for code validation a 3d
viscous computer simulation of this
inlet
revealed previously unknown strong
secondary flows
as can be seen from these particle
traces
these secondary flows are formed because
of shock wave
interactions with the turbulent side
wall boundary layers
and they create additional inlet losses
the close coupling between analysis and
the validation experiment
was designed to confirm both the cause
and effect
of these previously unknown secondary
flows
a second important application of
computational fluid dynamics
is to analyze new concepts in propulsion
such as this supersonic fan blade
designed using a 2d
analysis a 3d viscous computer
simulation
predicted blade pressures shown here in
varying colors
the simulation also allowed designers
and engineers to visualize secondary
flow
here particle traces show the passage
vortex
which can be traced to its origin as a
horseshoe vortex
ahead of the blade a third application
of computational fluid dynamics at nasa
lewis research center
lies in the study of interactions which
are difficult to measure
such as this supersonic combustor
the combustion process shown was modeled
as two hydrogen jets
operating at a pressure ratio of eight
and injecting into a rectangular duct
compression waves are generated upstream
of each
jet as can be seen from these color
contours
on the top wall the two jets create an
adverse pressure gradient which causes
the free stream particles to move
outward laterally
as well as downward the jets are bent
by the free stream the second jet
penetrates more deeply
into the free stream flow than the first
jet
deeper jet penetration means enhanced
mixing of hydrogen
and air and consequently more complete
combustion computational fluid dynamics
is also being used
to study the interaction of the external
environment
with a propulsion system in this example
an under expanded 3d asymmetric nozzle
at a pressure ratio of 10 exhaust
supersonically into quiescent air
nozzle flow expands laterally downstream
of the lower lip compression waves
reflect
off the upper and lower shear layers and
a very thin
shear layer emanates from the side wall
the high temperature high stress
requirements of modern aircraft engines
necessitate the development of novel
materials
the study of which can greatly benefit
from computational material science
metals ceramics polymers and composites
of these
are all employed to satisfy the high
temperature
strength and durability requirements
material science is concerned with
phenomena that range from rapid material
processes
with solidification rates measured in
meters per second
in melt spinning to deposition rates of
microns per hour
in chemical vapor deposition
in chemical vapor deposition high
temperature coatings
fibers and semiconductors such as
silicon carbide are
made this process involves injecting a
nutrient gas
into a reactor in which the gas then
undergoes several
gas phase chemical reactions as it
passes across
a heated susceptor subsequent surface
reactions deposit the needed materials
in this case silicon on the susceptor
the computer simulation shown includes
the 3d aspects of the reactor
strong natural buoyancy causes
substantial distortions of convecting
fields
shown here as path lines of neutrally
buoyant particles
subsequent distortions in both the
temperature and reacting species fields
are evident resulting in severe
non-uniformities
in coating thickness and structure
additional analyses show an excellent
agreement between the experimental and
numerical deposition rates on the
susceptor
this study shows that computational
material science
can provide information important for
the understanding
and design of new materials
the nasa lewis research center couples
computational and experimental programs
for efficiently meeting the requirements
of modern aircraft engines
the development and practical
application of advanced numerical
simulation codes
for propulsion systems will require
increases
in computing power that is speed
and memory these advances will have to
be matched by improvements in
computational support
program development and computer
graphics
the graphics tools are especially
important because of the massive amounts
of data that need to be understood
the lewis goal in scientific computing
is to provide high performance graphics
workstations
having access to parallel processors
mainframe
and supercomputers nasa lewis research
center is moving as rapidly as possible
towards the establishment of a
high-performance computing environment
that will satisfy the long-term
experimental
and computational needs of future
aircraft engine design
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