AeroRocket
Subsonic and Supersonic Wind Tunnel Testing
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Copyright © 1999-2008 John Cipolla/AeroRocket

SUBSONIC
WIND TUNNEL TESTING
The
AeroRocket subsonic wind tunnel
is a suction
system powered by a two speed 1/3 horsepower fan.
The test section is 7 inches wide x 10 inches high x 16
inches long. The
basic subsonic wind tunnel design is by
Donald D. Baals of NASA and was fabricated and
redesigned by John Cipolla using these
plans. A research quality pitot
tube is used to measure the difference between static pressure
and dynamic pressure in the wind tunnel. An analog velocity meter
is used to convert the resulting pressure differential between
the static and dynamic pressure to determine test section flow
velocity in feet per minute. Recently, the insertion of aluminum honeycomb
material before
and after the test section resulted in a significant increase in
measurement accuracy for drag and lift coefficients by
decreasing flow turbulence by several orders of magnitude.
Small wind tunnel models that represent
large designs are routinely tested in the AeroRocket subsonic
wind tunnel, below. More wind
tunnel testing information is available on the Spool Rocket Report
description web page.
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Basic Features
Velocity:
35 to 80 ft/sec with a test item installed
Reynolds Number: Laminar
and turbulent flow with trip wires
Test Section:
7 inches wide X 10 inches high X 16 inches long
Drag
(CD) and lift (CL) using 2-component force balance system
Unique wind tunnel model fabrication
skills

X-30 Wind Tunnel Model |

Subsonic Wind Tunnel |

HL-20 Wind Tunnel Model |
Flow Visualization
Smoke Flow
Visualization
Filament Probe Flow Visualization
Schlieren Photography for
Supersonic Flow
(presently
under development)
Support Systems
CD &
CL using rear mounted sting (0 to 40 degrees AOA)
CD & CL using vertical
mounted Sting (0,
5, 7.5, 10, 12.5, 15 and 17.5 degrees AOA)
Low turbulence due to very fine honeycomb flow straightener
before and after test section
Center of pressure location
measurement
(XCp)
SUPERSONIC SHOCK TUBE WIND TUNNEL TESTING
The AeroRocket shock tube provides supersonic drag (CD) measurements
from Mach 1 to Mach
5. This system is operational for supersonic
wind tunnel testing. AeroRocket's expertise in the fabrication of
miniature wind tunnel models allows testing realistic shapes for
accurate flow field, CD and CL measurements for a wide variety
of applications including development of the
HFV-3X spacecraft.
Contact AeroRocket

Please
contact
AeroRocket for a FREE quote.
Please see Ordering Instructions. |
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Wind Tunnel Testing Services
Customer Comment (10/06/2004)
Using the AeroRocket wind tunnel, I requested that John measure
the subsonic lift and drag coefficients of an unusually shaped
airship (V-Ship) in his wind tunnel. He made a model to our specifications,
and measured the key coefficients (CD and CL) as a function of
angle of attack, providing exactly what I wanted. In addition,
he calculated the lift and drag from first principles so he could
compare theory to experiment, provided a full report replete
with photographs of the model under test, and sent the model
mounted on a stand along with the report, all at very reasonable
cost. I recommend his services without reservation.
Michael Monsler, Ph.D.
Schafer Corporation, Livermore CA
VALIDITY OF USING SMALL MODELS TO
REPRESENT FULL SCALE VEHICLES
The full-scale
V-Ship was 60 meters long while the V-Ship model tested in the AeroRocket wind tunnel,
second model from the left above, is only 3.5 inches long. Therefore,
representations of very large objects may be
successfully tested in the AeroRocket wind tunnel at relatively
low Reynolds number as long as the flow is assured to be either
laminar or turbulent depending on the actual characteristics of
the full-scale flow. Small models that represent large designs are
routinely tested in the AeroRocket wind tunnel because aerodynamic shapes including
plates, spheres and cylinders exhibit relatively constant drag
coefficient (CD) over a wide range of Reynolds number as long as
the flow is turbulent or made turbulent using a trip wire. In
the illustration below, please notice that a 2-D plate normal to
the flow has a relatively constant CD for Reynolds
number ranging from approximately 1,000 to nearly seven million.
Similarly, cylinders have relatively constant CD for Reynolds
number ranging from approximately 1,000 to nearly one
million. The
phenomena of constant CD over a wide range of
Reynolds number is also valid for 3-D flow and is caused by the
transition to "forebody" turbulent flow at Reynolds number
1,000 and NOT any effect the base-region turbulent boundary layer
has above the critical Reynolds number for reducing base
drag. This
principal can be extended to many other complex designs where
shape and Reynolds number must be maintained for valid wind
tunnel results based on flow similarity. Please read Fluid Dynamic Drag by S.F.
Hoerner, pages 3-7 to 3-15 for more explanation.
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Drag (CD) verses Reynolds number (Re) for 2-D flow over common
aerodynamic shapes. |
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Wind
Tunnel Testing ($25.00/hour)
BACK
AeroRocket can assist you in determining Drag (CD), Lift
(CL), pitch-moment (CM), lift slope (CLa) and pitch-moment slope (CMa) for almost any aerodynamic shape utilizing its own
subsonic wind tunnel and two-component force measurement system.
The wind tunnel at AeroRocket's disposal was developed
in-house to provide a wide range of drag, lift, velocity and
pressure profile measurements. The test section is 7 inches wide x 10
inches
high and is 16 inches long. Maximum test section velocity is 80 ft/sec
with a test item installed. The AeroRocket wind tunnel
is ideal for measuring subsonic drag and flow visualization of
unusual rocket designs like the SS1 and shapes not treated by AeroDRAG
or any other rocket analysis computer program until the development
of AeroCFD and VisualCFD.
The AeroRocket
subsonic
wind tunnel is ideal for measuring drag and lift using the in-house
built two-component force measurement instrumentation system.
Basic
Cost Information
Subsonic Wind Tunnel:
Cost for using the AeroRocket
subsonic
wind tunnel is $25 per hour and reflects a 50% reduction
from the normal AeroRocket consulting fee of $50 per hour. The
AeroRocket subsonic wind tunnel testing fee includes set-up time, aerodynamicist
labor required to operate the wind tunnel and data presentation.
Set-up typically takes one hour and actual measurement
time will vary depending upon the number of measurement points
requested. For drag and lift wind tunnel testing at a single
angle of attack, total wind tunnel time is approximately 3 hours
for a total of $75 when utilizing a customer supplied wind tunnel model. For
more complex wind tunnel measurements, a customer supplied project
description and test matrix is required to accurately determine
total cost for wind tunnel usage. Please contact
AeroRocket to receive a cost estimate for your specific wind
tunnel requirement.
Supersonic Wind Tunnel: Cost for using the AeroRocket
supersonic shock-tube
wind tunnel is $100 per hour reflecting the labor
intensive nature of shock-tube wind tunnel testing. Presently,
measurements are limited to determination of drag coefficient
(CD) at Mach 1 to Mach 5. Measuring CL is a future capability
for the AeroRocket shock tube wind tunnel. Please contact
AeroRocket to receive a cost estimate for your specific
supersonic wind
tunnel requirement.
Model
Requirements
Customer's model must be 12 inches long
or less.
Customer's model over-all width
must be 3.25 inches or less.
Customer should supply a 1/4"
diameter mounting hole at the center of gravity of the model
to insert a sting for testing purposes. However, if the model
is not to delicate AeroRocket will drill the sting mounting hole.
AeroRocket will also supply the sting.
For supersonic wind tunnel
models please email for more information.
Wind
Tunnel Model
Fabrication
Subsonic Wind Tunnel: For a cost of only $50 per hour AeroRocket will fabricate your wind
tunnel model. Just mail or email your model's dimensions using
the requirements listed above as guidelines for model fabrication. A
Typical wind tunnel model can be fabricated in about 2 to 10 hours and will
cost approximately $100 to $500 depending on the level of detail
required. The HTV-3X, HL-20, X-30 NASP, X-43
and Sprint ABM wind tunnel
models pictured below were fabricated by AeroRocket. Wind
tunnel model fabrication costs in this group range from $500 for
the HTV-3X to $100 for the Sprint ABM.
Supersonic Wind Tunnel:
Supersonic shock tube wind tunnel models cost $100 per hour to
fabricate reflecting the difficulty in making miniature
supersonic wind tunnel models. A miniature shock tube wind tunnel model
like the HTV-3X pictured above costs $500 to fabricate.
Wind Tunnel Testing Ordering Instructions
BACK
Cost
for testing a customer supplied subsonic wind tunnel model is $25 per
hour. A typical series of subsonic wind tunnel tests as described in the
TECHNICAL DETAILS section cost approximately $250. Please
contact
AeroRocket for a FREE
quote for testing your specific model in the AeroRocket Wind
Tunnel. When contacting AeroRocket for the first time
concerning wind tunnel testing please
provide a "test matrix" that includes model configuration
(geometry), AOA, velocity, and whether the model is to be tested
using the vertical-sting or rear-sting mounting technique. Please
review the TECHNICAL DETAILS section prior to deciding which
type of mounting is appropriate. In addition, center of pressure
location testing and flow visualization testing are available
and illustrated below. Please contact AeroRocket by
e-mail
for prompt
attention to all wind tunnel testing requests.
Telephone requests for wind tunnel testing cannot and will not be accepted.
COST SUMMARY
Subsonic Wind Tunnel
Testing @ $25 per hour
Subsonic Wind Tunnel
Model Fabrication @ $50 per hour
Supersonic Wind Tunnel
Testing @ $100 per hour
Supersonic Wind Tunnel
Model Fabrication @ $100 per hour
(Please email for a FREE quote)

Wind Tunnel
Test Features
BACK
Wind tunnel measurements at a maximum wind speed of 80 ft/sec
(54.5 mph).
Drag (CD) and lift (CL) at 0,
5, 7.5, 10, 12.5, 15 and 17.5 degrees AOA using vertical-sting or rear-sting mounted
models for angles of attack ranging from 0.0 degrees to 40
degrees AOA.
Center of Pressure location (XCp)
measurement.
Flow visualization using probe-mounted
yarn filaments or smoke that define areas of reverse flow and vortical
motion corresponding to lift.
Experiments photographically
documented.
Turbulent flow measurement using
trip-wire if required.
Report summarizing the results.
Drag (CD) and Lift (CL) Coefficients BACK
Figure-1 illustrates the force balance
system used to determine rocket drag (CD) and lift (CL) of a
wind tunnel model mounted on a vertical-sting. Displacement in
the axial (drag) and vertical (lift) directions are measured
using the two load cells labeled DRAG and LIFT
respectively and then converted to drag and lift forces in Newtons
using the Vernier CBL-2 computerized data acquisition system.
The force balance system pictured in Figure-1 is designed to
separate the aerodynamic forces and the associated displacements
in the axial and vertical directions when the weight on the force-balance
plate causes the model to be freely suspended. Models tested
in the AeroRocket wind tunnel may be mounted on a vertical-sting
as in Figure-2 or mounted on a rear-sting as in Figure-3. Either
mounting configuration may be selected depending on the objectives
of the wind tunnel test.
Center
of Pressure (XCp) Location Measurement BACK
Center of pressure location measurements
are performed using a special XCp-Caliper that secures the model
in the wind tunnel test section using two opposing low friction
points. Figure-4 illustrates a ring-fin model rocket being tested
in the AeroRocket wind tunnel for the determination of center
of pressure location. The ring-fin model in this configuration
is stable because the support point is ahead of the actual center
of pressure. The actual center of pressure location (XCp) is
determined by moving the sting support location rearward until
the model becomes unstable and "noses over" to one
side or the other when the wind tunnel is operating. Figure-5
further illustrates how the ring-fin rocket model is secured
in place during center of pressure location testing. Please notice
the pitot tube used to measure the difference between static
pressure and dynamic pressure for determining flow velocity in
the wind tunnel. An analog velocity meter is used to convert
the resulting pressure differential to test section flow velocity
in feet per minute (fpm).

Figure-4,
Center of Pressure (XCp) Location Measurement

Figure-5,
XCp Measurement Instrumentation |
Filament Flow
Field Visualization BACK
A single-strand filament of low mass
yarn on a long slender probe illustrates the flow on and around
an object. Regions of reverse flow behind blunt bodies become
visible. Please refer to Figure-6, Figure-7 and Figure-8 to see
how the base flow of the Sprint ABM is investigated using a yarn
tuft on a probe. In addition, regions where the flow rotates
indicate stream wise vorticity and therefore lift and circulation.
Please refer to Figure-9, Figure-10 and Figure-11 to see how
the fin-tip vortical flow pattern of the X-43 at an angle of
attack of 15 degrees is investigated using a yarn tuft on a probe.
Please note the three photographs of the X-43 are of the yarn
filament as it rotates in the clockwise direction as viewed from
the front of the wind tunnel model.
FILAMENT FLOW VISUALIZATION

Figure-6,
Sprint ABM Base Flow on Rear-Sting Mount

Figure-7,
Sprint ABM Base Flow Circulation on Rear-Sting Mount

Figure-8,
Sprint ABM Base Flow Circulation on Vertical-Sting Mount

Figure-9,
X-43 Fin-Tip Vortical Circulation (1)

Figure-10,
X-43 Fin-Tip Vortical Circulation (2)

Figure-11,
X-43 Fin-Tip Vortical Circulation (3) |
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Smoke
Flow
Field Visualization
BACK
A smoke generator and blower are
used to test models outside the AeroRocket wind tunnel. Larger
models may be accommodated because the smoke visualization tests are
conducted without the constraints of the relatively small dimensions
of the AeroRocket wind tunnel's test section. Figure-12 and
Figure-13 display the vortex flow pattern from the leading edge of a
60 degree triangular wing.
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SMOKE FLOW VISUALIZATION

Figure-12, 60 degree Wing Tip Vortex Flow

Figure-13, Filmstrip of Smoke Visualization Testing
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PAST WORKS

Figure-14, AeroRocket
Wind Tunnel with X-43 mounted on vertical sting

Figure-15, Wind
tunnel models from past and present work

Figure-16, X-43
mounted on vertical sting
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