This technical paper presents an aerodynamic analysis of the effect of dimples on an aircraft wing. It discusses airfoil nomenclature and lift theory. The paper then examines boundary layer separation and how dimples can delay separation by creating vortices. Test results show that inward and outward facing compound dimples on a NACA 0018 airfoil increase its coefficient of lift and reduce coefficient of drag at high angles of attack. In conclusion, applying dimples to an airfoil's design can increase its stall angle and reduce aircraft take-off distances.

1. TECHNICAL PAPER PRESENTAITON ON
AERODYNAMIC ANALYSIS OF DIMPLE EFFECT
ON AIRCRAFT WING
PREPARED BY
PRADEEP KUMAR
R.No-2326
GUIDED BY
Prof U.V.AWASARMOL

2. AIRFOIL NOMENCLATURE
• Airfoil: 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 itself
• Leading Edge: Most forward point of mean chamber line
• Trailing Edge: Most reward point of mean chamber line
• Chord Line: Straight line connecting the leading and trailing edges
• Chord, c: Distance along the chord line from leading to trailing edge
• Chamber: Maximum distance between mean chamber line and chord line
Measured perpendicular to chord line

3. 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.

4. STARTING VORTEX

5. ANGLE OF ATTACK Vs LIFT
Angle 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.

6.  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.

7.  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.

8. 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.

9. 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

10. RESULTS AND DISCUSSION-
EFFECT ON CL

11. EFFECT ON Cd

12.  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.

13. THANK YOU