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General
Mounting Information
Model mounting or support systems vary widely
depending upon the objectives of a given test program. For
tests requiring the acquisition of force and moment data, a
balance system will be required and the model must be
mounted in a manner to transmit all aerodynamic loads to the
balance. The majority of testing at the Oran W. Nicks Low
Speed Wind Tunnel involves models mounted on the external
balance located immediately below the test section.
Three basic methods of supporting the model
on the external balance are available:
The three strut system is comprised of two
main struts which may be spaced laterally from 9 to 66
inches apart plus a tail strut or pitch arm with a variable
location between 18 and 42 inches aft (or forward) of the
main struts. The purpose of the tail strut is to pitch the
model about the trunion of the main struts. The trunion
point is set at 42 inches above the test section floor and
corresponds to the moment resolving center of the external
balance. Fairings and dummy struts are available to allow
tare and interference measurements. This simplifies
assessment of mounting system effects so that they can be
subtracted from the test data. The two-strut system uses a
single main strut in conjunction with the pitch strut. It
should be noted that for this type of support system, the
main strut must take all lateral and rolling loads as the
pitch strut has little lateral stiffness. The single strut
support system makes use of one main strut in the testing of
models with internal pitch mechanisms.
For models that do not require pitch changes
one or two main struts can be used to mount the model
depending on the size of the model. A
fast turntable strut can be
used on models that are mounted on one strut in the center
of the main turntable or offset towards the test section
exit. The fast turntable allows faster setting of yaw
angles. For offshore structures a special mounting system is
employed using the fast turntable strut offset towards the
test section exit.
Sting mounting systems are currently
available for testing models using internal strain gage
balances mounted on a single axial support. A
large sting mount adapts to an
adjustable knuckle. This can be used with a sting sized for
a 2" or a 1.25" diameter balance. (These larger
balances are not provided by the facility.) Models mounted
with wings vertical can be pitched using the test section
turntable, and yaw can be combined with pitch by adjusting
the knuckle. The angle range for the knuckle is -2° to +20°.
A small sting mounting system is
also available using a 1.25" diameter balance. Offset angles for
this knuckle can be set from -1° to +30°. The
HARS robotic
sting is also available for sting mounting models.
Internal balances are available for the small sting and
HARS.
For test programs
not requiring
the acquisition of balance data, models may be mounted
directly to the walls or floor of the test section, to the
turntable, to the balance struts with the balance locked, or
to a ground plane. The
ground plane may also be used with strut balance mounting
systems.
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Three
Strut Mount
Three strut mount with nose strut.
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Two
Strut Mount
Two strut mount with tail strut.
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Single
Strut Mount
Testing a prototype on the single strut mount.
The single strut support system makes use of
one main strut in the testing of models with internal pith
mechanisms, or for models that do not require pitch changes.
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Internal Pitching Mechanism Specifications |
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Range |
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Lift Force |
±500 lbs. |
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Side Force |
±500 lbs. |
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Drag Force |
±500 lbs. |
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Pitching Moment |
±50 lb-ft. |
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Rolling Moment |
±100 lb-ft. |
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Yawing Moment |
±100 lb-ft. |
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Pitching Angle |
±40° |
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Pitching Speed |
1.5°/sec. |
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Fast Turntable
Oil Rig Mounted on Fast Turntable in Offset
Position.
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Large Sting
Large sting mount with 1.5" sting.
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Small Sting
Model mounted using small sting.
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High Attitude Robotic Sting (HARS)
Click here for more
information on HARS
Model mounted to HARS for angle of attack sweeps.
HARS is a sting mount that
allows changes in the yaw, pitch, and roll angles for the
model during actual testing.
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Bicycle Mount
Click here for more
information on Bicycle Testing
Bicycle test using two strut mount and flow
visualization.
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Offshore Mount
Click here for more
information on Offshore Structure Testing
Oil rig mounted on fast turntable in
offset position with boundary layer fence.
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Ground Plane
Mount
Ground plane with single strut mount.
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Mount Not Requiring Balance Data
Aluminum siding test with structure mounted directly to wind
tunnel walls.
Endurance test of palm frond subjected to
high wind.
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Tare
and Interference Mount
Dummy struts attached to model for tare and
interference runs.
Fairings and dummy struts are available to
all tare and interference measurements. The image
system simplifies assessment of mounting system effect so
that they can be subtracted from the test data.
Because there is no turntable in the ceiling, the image
system for the three strut mounting system cannot implement
changes in yaw angle.
Inverted model using a single strut mount
with dummy strut attached for tare and interference runs.
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