APPLIED FLUID MECHANICS
C2 Subsonic Wind Tunnel - Issue 13
The Armfield Wind Tunnel provides a comprehensive facility for the study of
subsonic aerodynamics. The performance of the tunnel and its instrumentation
also make it suitable for simple research projects.
ORDERING SPECIFICATION
> Self-contained wind tunnel for the study of subsonic aerodynamics, complete with two- component balance system and air speed indicator
> Special features:
- Contraction and Diffuser: precision glass fibre mouldings
- Test Section: clear acrylic, which retracts to permit access to the models.
- Adjustment of models can be made with the tunnel in operation.
- Fan: Variable speed motor driven unit downstream of the working section permitting
stepless control of airspeed between 0 and 26ms-1
- Balance: Lift and drag Lift
- 7.0N, Drag
- 2.5N, Sensitivity ±0.01N
- Air speed: Indicated on inclined manometer directly calibrated in m/s
- Support structure: A strong steel frame including working surface and fitted
with castors for easy movement
> Suitable for undergraduate and simple research work.
> Working section: 304mm wide x 304mm high x 457mm long (octagonal cross- section)
> Contraction area ratio: 3:1
> Motor rating: 1.5kW
> A user instruction manual is supplied
> Optional models and instrumentation allow:
- Investigation of the development of the boundary layer on a flat plate by
measurement of total head distribution
- Flow visualisation studies around an aerofoil
- Measurement of pressure distribution around an aerofoil at various angles
of attack or around a cylinder
- Measurement of lift and drag on an aerofoil with leading edge slot and trailing
edge flap
- Velocity and pressure distribution measurements using a pitot static tube
and yaw probe
- Measurement of drag for models of different shapes but common equatorial
diameter
- Demonstration of flutter of an aerofoi
- Calibration of the wind tunnel velocity indicator using a pitot static tube
- Investigation of the wake behind a cylinder or aerofoil using a wake survey
rake
Demonstration and Measurement Capabilities
A wide range of measurements and demonstrations is possible with the
equipment. A selection using the models and instrumentation provided
are:
> investigation of the development of the Boundary Layer on a flat
plate by measurement of the total head distribution
> flow visualisation studies around an aerofoil
> measurement of pressure distribution around an aerofoil at various
angles of attack
> measurement of pressure distribution around a cylinder
> measurement of lift and drag on an aerofoil with leading edge slot
and trailing edge flap
> velocity and pressure distribution measurements using a Pitot static
tube and yaw probe
> measurement of drag for a selection of models of different shapes
but common equatorial diameter
> demonstration of flutter of an aerofoil
> calibration of the Wind Tunnel velocity indicator using a Pitot
static tube and inclined manometer
> investigation of the wake behind a cylinder or aerofoil using a wake
survey rake
Description - C2-10: Subsonic Wind Tunnel
The Armfield Wind Tunnel is simple and safe in operation. It is
supplied as a complete self-contained facility mounted on castors for
ease of movement. Main equipment comprises the tunnel with a
two-component balance system and an air speed indicator.
Air enters the test section through a carefully designed contraction
followed by an aluminium honeycomb flow straightener designed to
ensure that the flow is steady in both magnitude and direction and has
a flat transverse velocity profile. A low angle diffuser at the outlet
end contributes to flow stability in the test section. A five bladed
fan is located at the outlet of the diffuser section. The fan is
driven by an AC motor supplied from an inverter speed control unit,
allowing smooth control of air speed.
The parallel octagonal test section is manufactured from clear acrylic
and may be retracted on rails to permit unobstructed access to the
models.
The two-component balance consists of a pair of balances supported on
knife edges on mutually perpendicular axes parallel to and normal to
the axial centre of the tunnel. Lift and drag components of force
exerted on the models under test are balanced by sliding weights along
the arms of the balance until a state of null deflection is reached.
Graduations in units of force allow lift and drag to be read directly.
The complete assembly is linked to a simple oil filled damping pot.
Models are mounted on the balance within the working section and a
protractor with cursor allows angles of incidence to be changed
quickly and accurately while the tunnel is running.
The accuracy of the tunnel and its instrumentation make it suitable
for undergraduate and simple research work.
A comprehensive range of accessories is available for use with the
tunnel:-
C2-13: Multi Tube Manometer
This is an inclinable manometer board equipped with 20 tubes, acrylic
manifold and a reservoir mounted on a vertical rod such that the
position of the datum manometer tube levels may be adjusted to
convenient heights before commencing experiments.
Scale length is 370mm accommodating measurement of pressure up to
290mm water gauge.
This general purpose kerosene manometer is suitable for use with many
Armfield model accessories requiring pressure measurement (kerosene
supplied).
C2-14: Pressure Wing, Cylinder, Wake Survey, Rake & Flow Visualisation Kit
The wing profile is based on the NACA 0015 aerofoil section with chord
length of 100mm. Eleven pressure tappings, all perfectly flush with
the wing surface are distributed around the profile and fitted with
flexible tube designed to be connected to the multi tube manometer
C2-13. All the tubes are housed inside the wing to avoid interference
with the air flow.
The wing position can be adjusted and one of the two end plates is
graduated so that the angle of attack can be read directly. The wing
is also fitted with an acrylic visualisation plate on which a
graphite/kerosene mixture can be used to show the lines of flow. A
supply of this mixture and other accessories are also provided. An
eighteen tube wake survey rake is provided together with a 25mm
diameter cylinder so that its wake may be compared with that of the
aerofoil.
C2-15: Aerofoil with Slot & Flap
The aerofoil, accurately machined to NACA 0015 profile, is equipped
with an adjustable leading edge slot and trailing edge flap.
It has a 63mm chord and a 250mm span. The flap is adjustable in
angular deflection and in clearance from the aerofoil.
Experimental results such as lift curve slope (corrected for aspect
ratio), maximum lift and maximum drag may be checked against NACA data
(NACA details not supplied).
C2-16: Pitot Static Tube
This item is of 4mm diameter stainless steel tube with a collet type
mounting chuck to facilitate full traverse across the working section.
It is of Prandtl design and may be used with negligible correction up
to angles of yaw of at least five degrees. As with the yaw probe,
C2-17, this instrument is designed to be used in conjunction with
other models where velocity and pressure distributions are of
interest. The multi tube manometer C2-13 is used to monitor the
pressure readings.
C2-17: Yaw Probe
This item is of 4mm diameter stainless steel tube with a collet type
mounting chuck to facilitate full traverse across the working section.
It is of the three hole type with centre hole for total pressure
determination. It is provided with an aligning block with set screw to
permit calibration in the wind tunnel. The multi tube manometer C2-13
is used to monitor the pressure readings.
C2-18: Drag Models
Five models, designed to be mounted in the lift and drag balance and
all of the same equatorial diameter, are provided:
> sphere
> hemisphere, convex to airflow direction
> hemisphere, concave to airflow direction
> circular disk
> streamlined shape
A spare support rod is provided for drag calibration purposes.
C2-19: Pressure Cylinder
The polished cylinder of 50mm diameter is provided with 19 equi-spaced
tapping points around the circumference, i.e. at ten intervals between
0° and 180° inclusive. The model is designed to be mounted vertically
and pressure tapping points taken through the cylinder are connected
to a series of flexible tubes suitable for the multi tube manometer
(C12-13).
C2-20: Flutter Wing
The flutter wing is constructed of solid balsa wood and is a two
dimensional symmetrical aerofoil to NACA 0015 specification.
The aerofoil has aluminium end plates and is supported at each corner
by two springs. These eight suspension springs simulate the flexural
and torsional structural characteristics of a real three dimensional
wing.
Angle of attack is adjustable. The flutter air speed may be determined
experimentally and the value compared with a calculated one.
Requirements
Electrical Supply:
C2-10-A: 220/240V/1ph/50Hz
C2-10-B: 120V/1ph/60Hz
C2-10-G: 220V/1ph/60Hz
Optional Accessories
C2-13: Multi tube manometer
C2-14: Pressure wing, cylinder, wake survey, rake & flow visualisation kit
C2-15: Aerofoil with slot and flap
C2-16: Pitot static tube
C2-17: Yaw probe
C2-18: Drag models
C2-19: Pressure cylinder
C2-20: Flutter wing
H14/2: Computer compatible manometer bank
Complementary products
C1: Compressible Flow Bench
C3: Multi-pump Test Rig
C4: Multi-purpose Teaching Flume
C6: Fluid Friction Measurements
C7: Pipe Surge and Water Hammer Apparatus
C9: Flow Meter Demonstration Apparatus
C10: Laminar Flow Table
C11: Pipe Network Apparatus
F6: Air Flow Studies
F14: Hydrogen Bubble Flow Visualisation System
Shipping specification
Volume 4m3
Gross weight: 430kg
Overall dimensions
Length 2.98m
Width: 0.8m
Height: 1.83m
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