3. INTRODUCTION:
A wind tunnel is a device which is used to study the effects of the air moving past
the solid objects.
When a vehicle is moved ,the air exerts forces against the moving vehicle.
This aerodynamic forces opposes the motion of vehicle, thus vehicle consumps
more fuel to travel distance at the same speed.Therefore there is a necessity to
study about these aerodynamic forces to determine ways to reduce the power
required to move the vehicle.
Not only in automobile field in architecture field also ,there is a need to
study the effect of air flows on the tall building and other constructions like bridge
etc. .If aerodynamic forces is not taken under consideration during designing then
the building and other constructions will collapsed when air flow with high velocity.
A wind tunnel is such a device or tool which is used for study the
aerodynamic forces on a moving vehicle and other constructions.
4. HOW DOES ITWORKS ?
In actual practise the vehicles move against the air but to perform study at one
place we will placed the object fixed in the wind tunnel and will make the air
flow over this object with the help of fan.
The airflow created by the fans that is entering the tunnel is itself highly
turbulent due to the fan blade motion and so is not directly useful for
accurate measurements.This turbulence of air is reduced by using honeycomb
and anti-turbulent screens which is installed at the inlet.
Because air is transparent it is difficult to directly observe the air movement
itself so to make it visualable we can use smoke, fog etc.
5. Contd..
To study the aerodynamic forces at different angle of attack a we will
provide a mechanism so that object can be tilt with in the wind tunnel to
make relative angle between air flow and itself.
To measure force and moment forced balanced we will provide a
mechanism in the tunnel with the help of which we will able to measure drag
force , lift force ,lateral force and many other phenomenon.
•
7. • The purpose of the inlet and settling chamber is to align and smooth the air flow
before it enters the contraction part. It provides with the plastic honeycomb.
This honeycomb is consist of approximately 3600 individual cells, which serve
to minimize transverse fluctuations in air velocity and “knock down” larger
scale turbulent eddies. Two anti-turbulence screen is also used to further
reduced the turbulence intensity.
•
•
•
•
•
• The purpose of the contraction is to smoothly accelerate the air exiting the
(larger) inlet/settling chamber and direct it into the (smaller) test section. In the
process, turbulence intensity is further reduced, as the overall mean velocity
increases while near-instantaneous variations in velocity are little affected.
8. •
• In the test section the test over the object is performed. The object is
located at the centre of this section. Front and rear sides should be
transparent so that we can see the flow of air over objects.
•
• To make air visible we can use smoke.
•
• An anemometer is provided at the end of test section which is used to
measure the velocity of flow through the test section.
•
• The purpose of the diffuser is to allow the air exiting the test section to
expand and gradually slow down, thus reducing the dynamic pressure
(kinetic energy) and increasing the static pressure.This reduces the current
drawn by the fan motor or, alternatively, allows a higher speed to be
achieved for a given motor/fan size and current draw.
