Abstract
In this
experiment we will understand how an airfoil can generate lift and lift
theories and will obtain a NACA 2412 characteristics using a model airplane
with a slab at different speed and angles of attack experimentally using the
wind tunnel. And then we are going to compare these results with the same
conditions but from different sources using XFLR5 and standard data from NACA.
Introduction
“An airfoil-shaped
body moved through a fluid produces an aerodynamic force. The component
of this force perpendicular to the direction of motion is called lift. The component parallel to the direction
of motion is called drag.” [Wikipedia]
Airfoils are
found in helicopter rotor blades, propellers, fans, compressors and turbines.
Sails are also airfoils, and the underwater surfaces of sailboats. Also it is
found in swimming and flying creatures and even plants and sessile organism and
the bodies of fishes. Also used in automobiles and spoilers to create a down
force improving traction.
Airfoils tents
in the wind tunnel are simplified assumptions near to the theoretical results; they
ignore the effect of viscosity, nonlinearities in the equation of motion,
three-dimensional effects, unsteady flow, free stream and turbulence and wing surface
roughness.
Various terms are related to airfoils are defined below
- · The mean camber line
- · The chord line
- · The Chord
- · Leading edge
- · Trailing edge
- · The aerodynamic center
- · The center of pressure
:main tybe of airfoil is
- · Symmetric / cambered
- Subsonic/ supersonic/ supercritical
Discussion
As angle of attack increase the lift
coefficient increase till stall.
As the speed increase (Reynold number increase)
the drag increase and CL max decrease.
As the speed increase the zero lift angle
decrease (the slope shifts to the left)
How can a negative camber or a negative angle
of attack produce lift?
The angle of attack is a combination of an
induced angle and an effective angle of attack.
The wing is attached to the fuselage at a
certain angle more than zero. So it has by default an angle of attack.
A negative angle of attack produces lift
because the effective angle of attack is indeed positive
Conclusion
The standard
data are the most accurate and then the data from the XFLR5 with slight
variance in the data from the software.
Both the software and the experimental are close and acceptable in comparing between them.
EmoticonEmoticon