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Frank Wenham
Frank Wenham
Benjamin Robins
Benjamin Robins
George Cayley
George Cayley
Osborne Reynolds
Osborne Reynolds
Hiram Maxim
Hiram Maxim
Wright Brothers
Wright Brothers
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Introduction
Introduction
What is a Wind Tunnel?
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a facility that provides a controllable
flow field for investigating various flow
phenomena and testing aerodynamic
models
a tool used in aerodynamic research
to study the effects of air moving past
solid objects
*** Advantage: experiments can be performed under well-controlled
flow circumstances compared to open environment experiments
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Aeronautical Wind Tunnels
Automobile Tunnels
Aeroacoustic Tunnels
Classifications of Wind Tunnel
Classifications of Wind Tunnel
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Aeronautical Wind Tunnels
Aeronautical Wind Tunnels
High Reynold’s Number Tunnels
Pressurized Tunnels
Heavy Gas Tunnels
Cryogenic Tunnels
High-altitude Tunnels
V/STOL Tunnels
Spin Tunnels
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Tunnels are also classified by flow speed:
Subsonic (M<.8),
Transonic (.8<M<1.2),
Supersonic (1.2<M<5.0), or
Hypersonic (M>5.0)
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Wind tunnels may also be classified according to their
air pressure:
atmospheric
variable- density
or their size:
ordinary
full-scale
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Elements of a
Elements of a
Wind Tunnel
Wind Tunnel
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straightens the airflow
*** The less turbulence there is, the
better the wind tunnel will simulate
actual flying conditions
usually includes a honeycomb flow
straightener and wire mesh
smoothing screens that produce a
smooth airflow; effective at reducing
swirling currents in the tunnel airflow
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*** purpose: take a large volume of low-velocity
air and reduce it to a small volume of high-
velocity air
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models of wings or planes are placed here
*** As airflow is brought to the
desired velocity, sensors measure
forces, such as lift and drag, on the
test article.
Lift is the force on the wing opposite the force of gravity.
Lift holds a plane in the air.
Drag is the force on the wing in the direction of the
airflow. An engine must overcome this force to move a
plane through the air.
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Shapes of Test Section
Shapes of Test Section
Rectangular (General Purpose)
Circular (Axisymmetric Model)
Elliptical (Aircraft Model)
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where the air coming out of the test section
slows down prior to exhausting or
recirculating
a device to lower the air flow speed,
consequently reduce the pressure loss due
to friction
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provides the force that causes air to move
through the tunnel
*** Fan drive: provide a
pressure increase of
flow, to overcome the
pressure loss in the
tunnel circuit.
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Types of Wind Tunnel
Types of Wind Tunnel
Closed-type
Open-type
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Blowdown
Shock Tube
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Open-type Wind Tunnel
Open-type Wind Tunnel
also called an Eiffel tunnel
open on both ends and draws air
from the room into the test section
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Advantages
Advantages
Low construction cost.
Superior design for propulsion and smoke
visualization. There is no accumulation of exhaust
products in an open tunnel
Disadvantages
Disadvantages
Poor flow quality possible in the test section
High operating costs
Noisy operation
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Closed-type Wind Tunnel
Closed-type Wind Tunnel
also called an Prandtl tunnel or Gottingen tunnel
*** Air is conducted from the exit of the test section
back to the fan by series of turning vanes; air is
returned to the contraction section and back to the
test section; air is continuously circulated
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Advantages
Advantages
Superior flow quality in the test section
Low operating costs
Quiet operation
Disadvantages
Disadvantages
Higher construction cost
Inferior design for propulsion and smoke visualization
Hotter running conditions than an open return tunnel
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has a high pressure vessel upstream of the test
section and a low pressure reservoir downstream
of the test section
used for supersonic testing.
Blowdown Wind Tunnel
Blowdown Wind Tunnel
used for hypersonic testing
Shock Tube
Shock Tube
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Advantages
Advantages
High Mach capability
Lower construction and operating costs.
Superior design for propulsion and smoke visualization
Smaller loads on model during startup because of faster
starts
Disadvantages
Disadvantages
Shorter test times require faster (often more expensive)
instrumentation.
Need for pressure regulator valves.
Noisy operation.
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used to study aerodynamic flow under a wide
range of temperatures and pressures that are difficult
to obtain in other types of testing facilities;
are also used to investigate compressible flow
phenomena and gas phase combustion reactions
Shock Tube
Shock Tube
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