you
at NASA Ames Research Center our basic
product is information information is
produced in the form of reports
technical reports publications and also
computer software we export hundreds of
computer programs each year to the
aerospace industry to be used by them to
help them in their design process of
various vehicle components or
configurations the technology developed
here at NASA Ames Research Center in the
form of computational simulation
software can benefit the aerospace
industry by helping them produce safer
and more fuel-efficient aircraft and
also producing those aircraft at a
reduced cost
there are basically three aerodynamic
simulation scientists that exist there's
flight testing there's experimental
testing and then there's computational
fluid dynamics each has its advantages
and disadvantages used together that's
what we call computation to flight which
is one of the visions at NASA's Ames
Research Center computational fluid
dynamics is used to complement both
experimental and flight testing we can
sometimes use computational fluid
dynamics to do smart experimental
testing in other words eliminate the
need for doing a lot of repetitive
testing and only test at very important
or very critical test conditions we can
do the same thing with flight testing as
you know flight testing is a very
expensive process we can use
computational fluid dynamics to help
augment that testing program and the
data that it's produced the computers
that are used to generate some of the
results that you see today are contained
in our NASA building the numerical
aerodynamic simulation facility they
included a crate to computer and a Cray
ymp computer these are two of the
fastest computers in the world today the
process by which we perform CFD
simulations involves first of all
defining the geometry forgetting
that geometry into the computer the next
step involves discretizing the flow
field about that configuration once that
flow field is discretized then we can
apply a flow solver in order to compute
the flow about that configuration that's
generates an enormous amount of data and
we use graphics workstations to reduce
that data and produce the results once
that technology has been validated
against experimental data and we
disseminate that technology for
industries use during launch of the
space shuttle provisions have been made
to employ an abort mode in case of
emergency one of the elements of this
abort mode is known as fast step fast
SEP is the fast separation of Shuttle
Orbiter from the rest of the launch
vehicle as the shuttle goes through the
launch sequence we will look at the
results of two different numerical
simulations the first occurs during
ascent as the shuttle passes through the
transonic range the external tanks of
the rocket motors experience a
hysteresis effect due to shock movement
since the Mach number is changing from
0.8 to 1.0 to over 6 seconds as shown
here the unsteady flow field that
evolves around the vehicle lags behind
what it would be for steady flow or a
fixed Mach number
notice the shock development shown by
the pressure contours on the leading
surface of the tank
on the base of the tank we see a highly
unstable flow regime
the second numerical simulation occurs
at about two minutes into the flight at
an elevation of about 50,000 meters at
this time the solid rocket boosters or
SRBs fall away from the tank and the
orbiter these bodies moving relative to
each other make analysis using other
methods much more difficult
notice the interaction of the pressure
contours as separation occurs visible
under the body of the shuttle are the
pressure contours created by shockwave
interaction between the orbiter the
external tank and the SRBs
Robert mecan research scientist and
member of the NASA Ames space shuttle
flow simulation team explains the work
done with a solid rocket booster or SRB
as a stepping stone to simulating fast
set K the work that the Space Shuttle
Group at Ames they interact with the
Johnson Space Center and we're doing
numerical simulations of various
conditions of the shuttle during during
the ascent of course there's a great
deal of wind tunnel data that's
available and also flight data that's
been accumulated over the flight history
of the shuttle and the shuttle group
here at Ames is augmenting the data that
there is they're filling in missing data
and carrying out calculations that
really aren't possible to model in any
other way path SEP being one of those
cases but really there's no other way to
get that sort of information
Computers now have primary controller
critics like turbo pump is the main
element in a rocket engine that supplies
fuel from the fuel tank to the
combustion chamber an important
component in the turbo pump is the
inducer a massive flow separation or
cavitation in the inducer can block the
fuel supply and result in total engine
failure see kwan-yuen a senior research
scientist of mcat institute at ames
research center explains a computational
study of this kind of problem was
impractical even on supercomputers since
the existing computer programs were not
fast enough the objective of our project
is to develop a very efficient computer
program which can give a direct impact
on the design of future rocket engines
shown here is the actual hardware of the
space shuttle main engine the turbo pump
consists of an inducer with a stationary
casing and a shrouded impeller with
partial blades in this
computer-generated image we remove the
shroud and view the inducer and partial
blades of the impeller
we can see a pressure gradient across
the blades as well as along the hub due
to the action of the centrifugal force
the particle traces over the suction
side of the blade and through the tip
clearance are seen here particles over
the pressure side of the blade shown in
purple are sucked into the tip clearance
and become the leakage flow the
streamwise particle flow is shown in
green the interaction of the leakage and
screen wise flows results in a region of
concentrated vorticity dough john kwok
research scientist with the applied
computation of fluids branch of Ames
Research Center and group leader for
this project continues the explanation
power pump is especially one key area we
can improve the performance aircraft
engine normally performs in the
efficiencies in the 90 percentile range
typically total pumper operates in 80
percentile efficiency range so there
suddenly we can see lots of room to
improve so shuttle can be benefited by
this computational simulation and by
improving the performance and improving
their reliability and eventually we will
meet the high launch capability in the
future
recent advances in heart surgery have
led to the development of the artificial
heart and the use of artificial heart
valves at the same time technology
developed to compute the flow in
components of the space shuttle main
engine is being applied to simulate the
unsteady flow in the Penn State
artificial heart Joe John Kwok explains
NASA's involvement in this spin-off
technology in general we are interested
in reapplying NASA develop technology
especially the CFD technology can be
reapplied in many different instances
and artificial heart is that it it's
particularly interesting because it will
help national health problem and the
demand for this type of mechanical
device can really contribute to to human
health and also animal health in the
future
Chetan Kyra's and Stuart Rogers research
scientists were responsible for the flow
code on this project
Stewart Rogers further explains the data
we started with in this case was
basically taken straight off of
blueprints which were used to build
models of this heart which were tested
by Penn State given the blueprints from
that model we then generated a series of
codes which would then describe that
shape to the computer as a series of
discrete points once we had those
discrete points then our flow solver
could take them and compute the flow
inside the heart
here we see the main chamber of the
heart and the particle traces which
indicate the flow the color of the
traces indicates the release height at
the inflow valve opening this is the
computer-generated image of the tilting
disk heart valve this valve can be used
in conjunction with an artificial heart
or used as a separate device the inflow
conditions are specified at the entrance
for the valve opening and they are
specified at the exit for the valve
closing the tilting disk reacts from the
force is applied to it by the blood flow
the valve motion is made possible by
using the chimera grid embedding
technique
we can view valve operation from
different rotational views red particles
are released from the vertical plane of
the entrance and magenta particles are
released from the sinus region of the
aorta which is located just beyond the
tilting disk the flow between the disk
and the aortic wall is highly
accelerated these kinds of changes in
the local blood flow conditions can
greatly affect the blood structure
technology developments that result from
solving this problem will yield spin
back applications for other flow
problems associated with the space
shuttle main engine an important
contribution made by NASA to medicine
results in a contribution made by
medicine back to NASA science aiding
science through interdisciplinary
cooperation
the f-18 is a jet fighter currently used
by the United States Navy it is used in
air-to-air and air-to-ground fighter and
attack roles by the fleet it has a great
deal of maneuverability and performs at
high G's and at high angles of attack
Russell Cummings National Research
Council research associate explains why
the f-18 was chosen as a research
vehicle the f-18 because it's capable of
pulling such high manoeuvres and high
G's gets into regimes of aerodynamics
that other aircraft don't even
experience because of that we're using
it as a test bed and a computation basis
for producing predictions for close over
heinel attack aircraft the cfd process
begins when the aircraft manufacturer
supplies the surface geometry of the
aircraft to be studied from this
information a surface grid and a flow
field grid is created then flow solving
begins using the three-dimensional
partially flux split time marching F 3d
navier-stokes code predictions are made
for turbulent flow by using the Baldwin
Lomax turbulence model here we compare
the flow visualization around the 1/32
scale model of the f-18 in the eidetic
international water tunnel with the
computational results clearly vortices
from the fore body and wing leading-edge
extension or Lex can be seen
we visualize our numerical predictions
using a variety of methods including
simulated surface oil flows which help
us to see the primary and secondary
cross flow separation lines on both the
fuselage and the leading edge extension
we also use felicity density contours
which enable us to see both positive and
negative senses of rotation of vortices
we can further visualize vortices by
passing particle traces back through the
holistic on tours which help us see the
vortices as they pass back over the
fuselage the goal of the research is to
be able to predict the flow over a full
aircraft such as the f-18 so we can see
the interaction of things such as the
Lexx vortex as it comes up over on top
of the Lex runs down the body and
pinches on the vertical tail and
possibly cause a structural damage in
actual flight tests shown here on the
fa-18 high alpha research vehicle or
Harv note the effect of the Lex vortices
on the vertical stabilizer as Russell
Cummings continues there are flight
tests being currently conducted done at
Dryden and we're comparing our CFD
predictions concurrently with them
taking their data and it's very exciting
since I don't believe that very many
people have been able to do that before
to actually have their CFD predictions
hand in hand with flight test data and
as we've compared the two side-by-side
we've seen that the CFD has been able to
very well predict the type of
aerodynamics both for surface pressures
and off surface flow visualizations
a multi-stage compressor is used on jet
aircraft engines to compress the air
before it goes into the combustion phase
a multi-stage compressor consists of
many rotor stator pairs rotors are
rotating air foils and stators are
stationary air foils in a multi-stage
compressor you may have as many as
seventeen to twenty of these rotor
stator pairs
Karen Gundy Berlet research scientists
at Ames Research Center explains the
difficulty of doing research in this
arena
the goals of my project are to compute
the three-dimensional flow within a
multi-stage compressor and hopefully by
doing this we can understand the fluid
physics of the flow within the
compressor see if we can design
compressors that are much more efficient
and much more reliable while reducing
the weight and the size of the
compressor here we see the results of
this research these are the pressure
contours within the aircraft engine
compressor the flow is moving from left
to right low pressure is indicated by
blue whereas high pressure is indicated
by red the pressure contours show the
inviscid part of the flow field by
seeing the pressure difference across
each of the air foils you can see what
forces are occurring on the airfoil
notice that the pressure within the
system is quite unsteady as the pressure
rises from the first stage to the second
stage
these are the entropy contours within
the two-and-a-half stage compressor the
entropy shows that viscous part of the
flow field it points out the slow fluid
that sticks to the surface of the air
force
notice that the slow fluid is convected
back through the system for three or
four cord lengths in a multi-stage
compressor the flow within the latter
stages is much more complex than the
flow for the initial stages easily seen
here the entropy plot does a good job
showing the wakes due to the viscous
dissipation of the air next to the air
fourth as the wakes progress along the
surfaces of the airfoils note that there
are varying forces applied that tend to
twist and rotate the air ports in the
latter stages where there are many wakes
being conducted through the compressor
the forces are even more severe the flow
fields are very complicated and the
unsteady forces appear to be varying
quite rapidly there are is experimental
data available for this compressor
that's why we chose to can simulate the
flow within this compressor so far the
comparisons have been very good time
average pressures on the surface are
very close to the experimental values
awake average data is in good comparison
for computations where I have an
extremely fine grid in the second stage
of the compressor one of the directions
I see for computational fluid dynamics
in the future is in an area we call
multidisciplinary physics in that area
we combined not only the fluid equations
but the equations governing
electromagnetics or propulsions or
controls into one software simulation
tool in order to solve problems like
that the problems of multidisciplinary
fluid physics it's going to require
computers a thousand times faster than
the computers we have today computers on
the speed of 1 teraflop that's one
trillion floating-point operations per
second in order to obtain the 1 teraflop
capability that we'll need for
performing multidisciplinary simulations
it's going to require massively parallel
computers computers that have thousands
and thousands
of processors as compared to the ymp
which has eight processors the
internationalization of the aerospace
business is going to cause CFD to play
an even greater role in the simulation
sciences area our American aerospace
manufacturers are going to rely have
more heavily on computational fluid
dynamics to produce better and more
efficient aircraft in order to be
competitive with our overseas
competitors
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