this video supplement is composed of
eight sequences each of which is
referenced in the report these dynamic
demonstrations primarily of f-106 being
flight vapor screen images obtained
using a rotating light sheet have been
designed to provide insight into the
process of developing quantifiable
results from this data for a complete
description of the image data is
analysis and the analyses of other types
of data as well the formal document
should be consulted
this flight experiment was done in order
to examine vortical flow field
characteristics on a highly swept wing
at full-scale flight conditions an F
106b fighter interceptor airplane was
chosen because of its wide flight
envelope allowing data to be gathered
over a range of angles of attack and
Mach numbers as well as reynold numbers
the test aircraft was outfitted with
flow visualization equipment adapted
from wind tunnel experimentation a
rotating thin sheet of light was
produced by a mercury arc lamp with a
slit and lens arrangement this
illumination permitted the general
characteristics of the vortex made
visible by an trained seated vapor to be
recorded by two video cameras focused
over the wings upper surface flight
planning to obtain desired flight
conditions resulted in two types of
maneuvers 1g flight at various speeds
and altitudes and descending spiral
turns meteorological conditions were a
chief limiting constraint test
instrumentation onboard the aircraft was
restricted from flight through clouds or
precipitation flights could only be made
at night during periods of no moon
elimination to ensure sufficient
contrast to the video cameras the light
sheet and vapor generator were
controlled by an engineer in the aft
cockpit a video display showed the image
from either camera along with angle of
attack and light sheet position flight
data were recorded on board and
telemetered to a ground station at NASA
Langley the primary data collected was
video at night the wing was not visible
and only the light sheet and vapor
cross-section over the wing could be
seen on point data collection proceeded
with a light sheet sweep across the wing
as well as several discrete light sheet
locations for post flight analysis
additional flights were made during
daylight with an oil mixture painted on
the wing to show surface flow patterns
an integrated computer process combining
image processing computer graphics and
photogrammetric reconstruction
techniques was utilized to aid in
three-dimensional visualization of
images produced by the rotating light
sheet accurate surface definition of the
aircraft was simulated through original
engineering drawings including geometric
description of wings fuselage and
vertical tail all of which were
collectively rendered to produce a
smooth three-dimensional model an
additional input into this environment
was a set of parameters describing the
placement of the two cameras on board
the f-106 be several targets were placed
upon the wing upper surface and record
that's measured to facilitate the
calibration of the cameras the WHA video
footage captured by the cameras in
flight provided only qualitative
information as to the size and placement
of vortices above the wing each image
had a perspective distortion produced as
the light sheet rotates away from the
stationary cameras to account for these
irregularities and extract quantitative
geometric information from the images a
photogrammetric reconstruction technique
was developed this technique map each
point in the image plane of a camera to
a precise location in the plane of the
light sheet camera orientation and
imaging properties as well as white
sheet position and angle were measured
to provide accurate calculations once a
set of data for a specified test
condition was constructed the 3d
coordinate of any point in the flow
field could be determined vortex core
paths determined from image centroids as
well as the approximate reattachment
lines could be extracted and displayed
in simultaneously the same sequence of
operations was applied to the side
camera image such that both camera data
sets were combined into one interactive
display
selected frames from videotapes for each
flight were digitized on the data
visualization and animation labs video
image processing system the video image
processing system is a combination of
hardware and software designed to
provide interactive capability for
processing videotaped images of wind
tunnel or in flight experiments the
system controlled from a host computer
consists of an image processing system
video equipment and a real-time digital
disc the software interface is a
commercially available image processing
software system the system is designed
to accept common video formats including
the s VHS and VHS formats used in this
flight test the software allows VCR
control from the computer station video
footage is digitized and stored a
digital disc at 30 frames per second
once rendered to real time disk the
images are slowed down during playback
and examined in slow motion timecode
information appearing in the lower left
corner uniquely identifies each image
selected images were stored on a disc
for post-processing
with the use of extractor software the
poor locations for a vortex system were
determined by examining each printed
image the show movie of this directory
option enables an overall impression of
flow over the wing at the test condition
and allows the determination of how many
vortices are present and the progression
beginning with the first image to be
examined invoked the defined region of
interest for this image option and use
the mouse to circumscribe the region
where the core is thought to be located
the horizontal and vertical pixel values
for this core is saved however if other
cores are present on this image they
must also be determined and saved before
proceeding the same steps are repeated
for other images after all the images
for the data set up in process the wave
program is exited and the core pixel
values up to four sets per image are
moved to a permanent file to determine
the reattachment points the extractor
software is once again used the outer
part of the vortex is projected
vertically to the forward part of the
light sheet footprint this is followed
by a circumscription of a small region
on the footprint with the mouse after
the horizontal and vertical pixel values
for the pointer found they are saved
what other reattachment points are
present on this image they must also be
determined and saved before proceeding
prior to saving all these pixel values
consistency in the criterion used to
determine reattachment points is checked
these steps are repeated for the other
images after all the images for the data
set have been processed the wave program
is exited and the reattachment point
pixel values up to four sets per image
are moved to a permanent file
to display vortex flow features is
characterized by the vapor screen image
in poor location with reattachment
points in a three-dimensional mode a
Silicon Graphics iris workstation and
the flow analysis software toolkit
called fast was utilized once logged
onto the iris a remote login is done to
a host computer containing the image
files along with poor location and
reattachment point trials with a fast
script written for this purpose it is
simple to obtain the vortex system
features on a wing by keying in the
corresponding points this generates the
feature from both the top and side
cameras in terms of the
three-dimensional coordinates consistent
with the aircraft and then displays them
on the surface geometry by using the
capabilities of fast the resulting
three-dimensional representation would
be moved until it resembles the NASA
technical paper
in 1985 the stationary light sheet was
used to illuminate a fixed cross section
of a flow field above the wing of the f1
or 6 be a camera calibration was not
performed at the time of his flight thus
the photo prometric reconstruction
technique could not be applied spatial
information was obtained before the
flights by placing a physical grid of
regularly spaced 6 inch squares in
refrain of the light sheet when the grid
was photographed by the camera in its
flight position a prospective distortion
was introduced the distortion was
corrected using a warping procedure to
produce an image in which the gridlines
were regularly spaced the warping
technique was applied to selecting vapor
screen images from 1985 and the
resulting images were evenly distributed
across the light sheet plane to
reconstruct 3d coordinates when loaded
into the fast program the vapour screen
images produced by the stationary light
sheet in 1985 could be correlated with
those obtained from the rotating light
sheet of 1991 the vortex core paths and
reattachment lines extracted from the
1991 flight data could be displayed
simultaneously
with the enhancer software the vortex
system details can be enhanced the code
expects the user to key in the starting
and ending white sheet angles as well as
the filename containing the group of
files to consider the code displays all
the images in the group and asked
whether or not a particular image is to
be included for enhancement choosing the
enhance this image option for the first
image leads to yet another menu a three
by three smoothing on each image is
imposed a total of three times in
combination with the continued
enhancement to the image process option
the contrast stretch option is used to
spread the entire range of pseudo colors
in such a way as to emphasize the
existing gradation in this image the
contour option allows selected colors to
be set to black thereby forming contours
finally the save enhanced flight image
option is used which displays the image
with an identification code and then
saves it
the photogrammetric reconstruction
technique which maps vapor images onto
light sheet planes was extended to
project imagery onto any arbitrary
surface composed of polygons this
extension was specifically used to
project oil flow patterns videotaped by
the top camera onto the political model
of a wing surface vapor screen images
core paths and reattachment lines
extracted from the rotating light sheet
but then be displayed simultaneously for
a direct comparison this video
supplement has been designed to
demonstrate the computer graphics
capabilities utilized in developing data
which are presented in the report the
viewers reminded that this supplement
does not purport to present the complete
set of various data types or the
attendant analyses both of which are
contained on the NASA technical paper
therefore the view is referred to the
formal report for the complete
documentation of this work