AERO LAB Flashcards
(36 cards)
machines for producing controlled stream
of air flowing through tunnels of varying but
controlled sizes. This, in turn enables us to
study the effects of bodies moving through
air or the resistance to moving air of
manufactured models.
Wind tunnels
________ are facilities (circular, elliptical
or rectangular tunnels) in which the wind is
produced by fans or by compressed air to
study and measure the action of the air flow
around a solid. The test section is the part
of the circuit where the solid is studied.
Wind tunnels
– In most cases, powerful fans move air
through the tunnels.
– The object to be tested is fastened in
the test section as to prevent the stream
of air from moving the object.
– The object can be anything.
– routine testing of airframes to
fundamental research on the boundary
layer – the slow-moving layer of air
adjacent to any wind-exposed body
surface.
– Measurements of air pressure and
other characteristics at many points on
the model yield information about how
the total wind load is distributed.
Applications of Wind Tunnels
⬣ first to make use of the “Whirling arm”.
⬣ The machine had an arm with a length of 4 ft
spun around by a falling weight acting on a
pulley and spindle arrangement.
⬣ This brought light as to how different shaped
objects, when moving through air is affected
differently by air resistance, or “drag”.
⬣ what limited his experiments is the speeds
that the whirling arm can reach.
Benjamin Robins
⬣ wrote and published in 1759 a paper that
addressed the relationship between
pressure and velocity for objects moving
in water and air.
⬣ He had used a whirling arm device
to measure the drag exerted on a
surface by moving air.
⬣ created the drag equation
D=Cd(k)(S)(V^2)
John Smeaton
⬣ also used a whirling arm to measure the
drag and lift of airfoils. His whirling arm was
5 ft (1.5 m) long and attained top speeds of
about 10 to 20 ft/s (3 to 6 m/s).
⬣ 1804 unpiloted glider was built and flew
successfully based on test data gathered
from his whirling arm.
⬣ He identified two very important factors
that are related to flight.
George Cayley
⬣ Between 1866 and 1889, he built several
whirling arms, ranging from 6.5 to 23 ft (2 to
7 m) in diameter.
⬣ However, the tests he carried out with these
arms gave incorrect results for both flat and
cambered airfoils and led him to believe that
powered flight was highly unlikely.
⬣ became famous as the first man to launch
himself into the air, fly, and land safely using
a glider.
⬣ ”Sacrifices must be made.
Otto Lillienthal
⬣ Famous in his automatic machine gun
creations
⬣ also used a huge whirling arm to test
airfoils between 1872-1894 in his
helicopter experiment.
⬣ His version of the whirling arm had a
diameter of 64 feet with the arm boasting
elaborate instrumentation to measure
lift, drag, and relative air velocity.
Hiram Stevens Maxim
⬣ _______ built a large whirling arm with 60 ft
in diameter and was spun around by 10-hp
engine.
⬣ One of his experiments with the arm
attained speeds up to 100 mph.
⬣ Being located outdoors because of its huge
stature, the apparatus was frequently
disturbed by winds and the self-created
mass of air swirling around the arm which
threw off results from his own experiments.
⬣ Before1900s ______ and the Wright brothers
labouring to create powered controllable flight
but because of the whirling arm limitation, the
Wright brothers turned to the wind tunnel as
their major test facility.
Samuel Langley
⬣ was the first individual to design a wind
tunnel.
⬣ He had tried a whirling arm, but his unhappy
experiences impelled him to raise funds to
build a wind tunnel in 1871.
⬣ The tunnel was 12 ft (3.7 m) long and 18 in.
(45.7 cm) square.
⬣ A steam-powered fan drove the air through
a duct to the test section where the model
was mounted.
⬣ The air could travel at a maximum velocity of 40 mi/hr
(64.4 km/hour).
⬣ he tested a variety of surfaces in his tunnel,
measuring lift-to-drag ratios and testing the effect
of different aspect ratios.
Frank H. Wenham
⬣ Began experimenting with lifting curved
surfaces in the 1880’s
⬣ Unimpressed with Wenham experiments, he
tried to carry out tests similar to Wenham’s
with his own wind tunnel.
⬣ His tunnel was a box 6 ft (1.8 m) long and 17
in. (43 cm) on each side.
⬣ In his tunnel, he eliminated the
problems associated with airflow fluctuation
that troubled Wenham by using a steam
injection system to generate the airflow.
⬣ He directed a jet of steam through the box, blasting
a series of wing shapes that he placed inside the
tunnel.
⬣ The aerodynamic model to be tested was mounted
in the throat area, and the flow velocity would be
greatest there—up to about 41 mi/hr (66 km/hour).
Horatio Frederick Phillips
French Civil Engineer, in
1909, he built a small
wind tunnel at the foot
of the Eiffel Tower to
study the effect of the
wind on more precise
fixed points.
Gustave Eiffel
Built a wind Tunnel. It
operated from 1901-
1908, and despite
successful and
sophisticated tests, the
tunnel was eventually
shut down. He
became an adversary
of the Wrights in their
legal battles.
Dr. Albert Francis Zahm
October 1901 their
small wind tunnel was
created. 6” square
inside about 6 ft long,
with a glass top. The air
speed was estimated to
be 40 feet per second.
The Wright Brothers
Types of Wind Tunnels
Speed Regime, Geometry
Types of Speed Regime
Subso, Transo, Superso, Hyperso
Types of Geometry
⬣ Open Return (Eiffel type)
⬣ Closed Return (Prandtl or
Göttingen type)
⬣ Intermittent
⬣ Continuous
Speed Regime of Sonic
M = 1
Speed Regime of Subso
0 < M < 1.0
Speed Regime of Transo
0.8< M < 1.2
Speed Regime of Superso
1.2 < M < 5.0
Speed Regime of Hyperso
M>5
⬣ These are wind tunnels used to test
objects at low Mach numbers or
speeds slower than the speed of
sound and below sonic speed.
⬣ Categorized into either Low –speed
subsonic (M≤0.3) w/c air considered
IDEAL , and incompressible and
High-speed subsonic flows.
Subsonic
two types of subso
lowspeed and highspeed
