Introduction
Many
instruments may wear or need to be checked monthly, annually…etc. to avoid
hysteresis (deviations in readings taken downward and upward) and inaccurate
data. Calibration is the process of comparing the readings to standard data or
more accurate instruments to avoid deviation and errors in data.
“A wind
tunnel is a tool used in
aerodynamic research to study the effects of air moving past solid objects. A wind tunnel consists of a tubular passage with the
object under test mounted in the middle. Air is made to
Abstract
In this experiment we will calibrate
a subsonic (open circuit) wind tunnel reference velocity by finding the wind
tunnel factor (K) and we’ll check the flow uniformity using experimental method
and by using pitot static tube and a micro manometer.
It
is advised to wear ear protection due to the fan’s load noise. (More than
85dBl)move past the object
by
a powerful fan system or other means
Wind Tunnel
tests are user to study the aerodynamic and stability characteristics in
aircraft models, airfoils, automotive companies, structures…etc. and the
physics of fluids. It can predict the behavior of new designed models. It’s
economical, accurate and rapid. Saves money, time and lives.
CFD programs
came up in the early 70’s, a method that simulate almost ant model in the wind
tunnel test section with an accuracy very close and identical to the tests
performed in the wind tunnel. However, Wind tunnels still more accurate and
able to study any model unlike the CFD. They are affordable programs unlike the
wind tunnels that may coast hundreds of thousands minimum.
theory
Wind tunnel air velocity is determined by measuring the static
pressure at inlet to convergent cone and the static pressure ahead of the test
section. ]
Discussion
The slope of
the reference and actual speed in the wind tunnel factor. (See fig 4)
The wind tunnel
factor in the theoretical part (0.8479) was very close to the experimental part
(0.8423) with a percentage error of 0.66% which is acceptable.
If we
multiplied the actual speed by the wind tunnel factor we get the reference
speed with an error of 0.1% which is also neglected.
Uniformity
check was positive. (100% uniform) (See table 2)
Conclusion
In the aircraft
industries the acceptable error is zero percent. These deviations and errors
are neglected and acceptable due to human error in taking accurate readings and
calculations.
It’s advised to
calibrate such instruments to avoid deviations error in readings especially the
wind
tunnel to simulate what conditions a plane in going through accurately.
tunnel to simulate what conditions a plane in going through accurately.
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