Third Year Mechanical Technical Paper Presentation
- 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.
- 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