AIRFOIL NOMENCLATURE
TECHNICAL PAPER PRESENTAITON ONAERODYNAMIC ANALYSIS OF DIMPLE
EFFECT ON AIRCRAFT WING
PREPARED BYPRADEEP KUMARR.No-2326
GUIDED BYProf U.V.AWASARMOL
AIRFOIL NOMENCLATUREAirfoil: An airfoil is the 2D cross-section
shape of the wing, which creates sufficient lift with minimal
drag
Mean Chamber Line: Set of points halfway between upper and lower
surfaces measured perpendicular to mean chamber line itselfLeading
Edge: Most forward point of mean chamber lineTrailing Edge: Most
reward point of mean chamber lineChord Line: Straight line
connecting the leading and trailing edgesChord, c: Distance along
the chord line from leading to trailing edgeChamber: Maximum
distance between mean chamber line and chord line Measured
perpendicular to chord line
LIFT THEORY
Velocity of air above the upper suface is higher than that of
lower suface and because of this there is a low pressure region on
upper side and high pressure region on lower side.Due to pressure
difference there is an upward force acting on airfoil know as
LIFT.The component of force perpendicular to Lift is known as
DRAG.
STARTING VORTEX
ANGLE OF ATTACK Vs LIFTAngle of attack: Angle of attack is the
angle between the body's reference line and the oncoming
flow.Increase AOA is associated with increasing lift coefficient up
to the maximum lift coefficient, after which it decreases.
As the angle of attack of a fixed-wing aircraft increases,
separation of the airflow from the upper surface of the wing
becomes more pronounced, leading to a reduction in the rate of
increase of the lift coefficient.
-The critical angle of attack is the angle of attack which
produces maximum lift coefficient. This is also called the stall
angle of attack.
- Above the critical angle of attack, as angle of attack
increases, the air begins to flow less smoothly over the upper
surface of the airfoil and begins to separate from the upper
surface.
BOUNDARY LAYER SEPARATION
- A boundary layer is that layer of fluid in the intermediate
viscinity of a bounding surface where effects of viscosity of the
fluid are considered in detail.
- Separation takes place due to excessive momentum loss near the
wall in a boundary layer trying to move downstream against
increasing pressure called adverse pressure gradient.
PREVENTION OF BOUNDARY LAYER SEPARATION-
. By giving the profile of a body a streamlined shape. - This
has an elongated shape in the rear part to reduce the magnitude of
the pressure gradient.
. This is how an airfoil came into existence.
EFFECT OF DIMPLE ON NACA(0018) AIRFOIL-
NACA(0018) AIRFOIL-
.Dimple on airfoil creates vortices, which delays the boundary
layer separation..By doing this, pressure drag is reduced at high
angle of attack and angle of stall is increased.
Fig.-Inward placed compound dimple Fig.-outward placed compound
dimple
RESULTS AND DISCUSSION-
EFFECT ON CL
EFFECT ON Cd
CONCLUSION--As we have seen earlier, coefficient of drag is very
low for a dimpled aerofoil.-So with dimple design on airfoil ,
aircraft stall angle is increased.-So with this the airfoil take
off distance can be reduced.
THANK YOU
