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Activity 2 Wind tunnel
Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y
Eléctrica, Ingeniería en Aeronáutica, Técnicas de Medida y Laboratorio,
003, Alberto Guzman Martínez, 1864062, 21/03/2021
Resume- In this activity I will define the wind tunnel, it’s
classification, components and which physical quantities we can
study in this device
OBJECTIVE
The objective of this research is the definition and study of
everything that surrounds the wind tunnel as an important tool
in the development of new aeronautical technology.
I. INTRODUCTION
In 1746, the English engineer and mathematician Benjamin
Robins, developed a device that had a rotating arm and that
developed small, but notorious, speeds of between one and
two meters per second.
Some years later, George Cayley would develop a rotating
arm with which he would achieve higher speeds. Although
this could only be flown in a balloon, it was a good basis for
measuring air resistance.
The investigations continued and in the 19th century the first
wind tunnel itself would be developed. It was the British
Frank Wenham who introduced it to the Aeronautical Society
of Great Britain in 1871. From that moment to the present, the
use of wind tunnels has become popular in different areas of
the industry, such as in the construction of airplanes and cars.
III. PARTS OF A WIND TUNNEL
1. Driving mechanism: Mainly, they are fans that extract or
inject air into the circuit. They can be more than one fan,
depending on the tunnel requirements and the design of the
contraction cone and diffuser.
2. Grilles for air lamination: They have the function of giving
uniformity to the air before it passes through the shrinking
chamber. Hexagonal grating, also known as honeycomb
grating, is generally used. A tunnel can have several bars;
however, its length is an important factor to guarantee good
flow quality.
3. Diffuser: It is the transition zone between two sectors of
different geometry. One of its main functions is to reduce the
speed of the air before reaching the fan.
There are two types of diffusers, the outlet diffuser, and the
wide-angle diffuser. The first balances the pressure of the flow
thanks to its change in dimension. Wide angle diffusers are
located before the contraction chamber as an extra section to
balance pressures and velocities before reaching the test
chamber.
4. Settling chamber: It is located before the contraction
chamber; it is an area where the homogenization bars are
placed to reduce turbulence in the test chamber.
II. WIND TUNNEL
The wind tunnel is a device created for aerodynamic testing;
is a simulator that allows you to know the behavior of various
fluids in real time, based on the use of air and allowing
extrapolation of results to others fluent like water, as well as
experiencing and study the lift phenomena and drag, to be
applied to profile design aerodynamic.
5. Contraction chamber: Its function is to accelerate the air
flow and reduce the intensity of turbulence. Its design is
important, since it depends on this that the wind layers are
arranged correctly. Its design will depend directly on the speed
to be achieved in the test chamber, in order to calculate the
inlet and outlet dimensions.
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6. Test chamber: It is the area where measurements and
experimentation are carried out, it is usually square in shape
and of variable length. The flow in this section should be as
uniform as possible.
7. Corners: Its function is the deviation of flow within the
circuit, it is desired that the interference between the flow and
the corner is the least possible.
8. Transitions: These are parts that serve as connectors
between the sections of the wind tunnel.
This is the scheme of the AARL 6 transonic wind tunnel.
Supersonic wind tunnels: In this type tunnels you need to
recreate supersonic conditions to have supersonic flow. Sonic
conditions can occur only where the cross-sectional area of a
duct is minimum, so a supersonic nozzle is composed by a
converging duct where the subsonic flow is accelerated, a
throat where sonic velocity is reached and the duct where the
flow becomes supersonic.
IV. CLASIFICATION
There are several types of classification for wind tunnels, by
their type of circulation, type of test, classified by pressure,
however, we will focus on their classification by speed.
Low-speed subsonic wind tunnels: They operate in the
incompressible regime, with speeds below 100 m/s (M=0.3).
It’s drive system is typically an axial or centrifugal fan that
pulls air through the test section.
Hypersonic wind tunnels: They operate at design Mach
number exceeding 5. They feature solid-walled test sections
and require contoured nozzle, which are usually axially
symmetric rather than two dimensional.
Models tested in hypersonic wind tunnels are typically larger
than those tested in supersonic tunnels and can reach to 10%
of the test section area.
Advantages
Low construction cost, the
cost of the return duct is
saved.
Its design is superior for
smoke visualization.
Drawbacks
The flow quality entering the
inlet and moving through the
test section may be low.
High operation costs
Noisy operation
High-speed subsonic and transonic wind tunnels: In the
high-speed subsonic wind tunnels is possible to reach Mach
numbers between 0.4 and 0.75, this is the compressible
regime. In the transonic win tunnels is possible to reach speeds
close to the speed of sound, between 0.75 and 1.2 in Mach
numbers. In transonic tunnels the flow features both subsonic
and supersonic regions. Both type of tunnel is designed on the
same principles of subsonic tunnels.
V. QUANTITIES MEASURED ON WIND TUNNELS
Temperature: Temperature is a measure of the average
kinetic energy of the particles in the gas.
Velocity: Change of position per unit of time.
For these magnitudes, the use of anemometers is common,
such as the Kestrel 400, with which speed and temperature can
be measured. Also is used the venturi tube.
Flow: amount of flow that passes through a section of duct per
unit of time.
In the case of flow, it is typically to use flow meters, such as
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the variable area flow meter, or also known as a rotameter.
Pressure: It is the normal force, applied over the area of a
surface in aerodynamics this force is applied by air molecules.
In the case of pressure, the Pitot tube is the first option for the
quantification of this property.
CONCLUSIONS
When I fully entered the world of aircraft development, I
thought that the wind tunnel was something simple, I thought
that it was just an isolated place where prototypes of airplanes
were tested with a fan.
But, after doing this activity, I realize that the wind tunnel
requires too much work in terms of calculations, construction,
etc. Leaving in evidence once again, that the field of
aeronautical engineering is something quite broad and that it
requires a lot of care for its study.
REFERENCES
[1]
[2]
[3]
[4]
Anderson, J.. (1989). Introduction to flight. Estados Unidos: Mc-Graw
Hill.
Desconocido. (2017). LA HISTORIA DEL TÚNEL DE VIENTO.
Marzo
19,
2021,
de
Hurricane
Factory
Sitio
web:
https://www.hurricanefactory.com/madrid/es/news/more/la-historia-deltunel-de-viento
http://evirtual.uaslp.mx/Habitat/innobitat01/CAHS/SS%20Arq%20Arist
a/Proyectos%20de%20Investigaci%C3%B3n/Conjuntos/Simulador%20
aerodin%C3%A1mico%20(T%C3%BAnel%20de%20viento).%20AGG
J%20MGJF.pdf
https://core.ac.uk/download/pdf/47245284.pdf