7- LiftSQLiteStudioSQLiteStudioSQLiteStudio.pptx

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1. Flow over Immersed Bodies lift Lec – 7

2. Lift and Drag Lift and drag concepts Drag Friction drag Pressure drag Shape dependence Reynolds number dependence Surface roughness dependence Composite body drag Lift Aerofoil aerodynamics Boundary layer control Racing car aerodynamics 2

3. Aerofoil aerodynamics 3

4. aerofoil An aerofoil is a streamlined body that can generate significantly more lift than drag. Examples of aerofoils include: Airplane wings Propeller blades Helicopter rotor blades Sails Wind turbine blades 4

5. Dimensions 5

6. 6 Lift P Stall Lower surface Upper surface L L L L AOA > 15 o Lower surface Upper surface Nozzle Effect Venturi Effect

7. 7

8. NACA aerofoils 8

9. Boundary layer control 9

10. Boundary layer control Boundary layer control  The techniques that have been developed to manipulate the boundary layer either to increase lift or decrease drag. 10

11. Controlling transition by shaping the aerofoil 11 Transition point 25% of cord 50% Max thickness Adverse P.G. Adverse pressure gradient promotes instabilities and expedites (hasten) laminar-turbulent transition

12. Controlling transition by suction 12

13. Controlling transition by suction 13 Transition point

14. Controlling separation by suction 14

15. 15 By blowing jet The blowing jet helps to overcome the adverse pressure gradient that causes separation Blowing jet

16. 16 by variable geometry deflected nose Thin profile with deflectable nose No deflection  Separation occurs at leading edge. Nose deflected  Flow remains attached at leading edge.

17. by variable geometry vortex generators Vortex generators can delay separation by mixing high-momentum fluid from the outer flow with low-momentum fluid next to the airfoil surface. 17

18. flaps Flaps are hinged or retractable surfaces on the trailing edge of an aircraft's wing that increase lift and drag when deployed. 18

19. 19

20. by variable geometry: slots Blowing jets are created naturally. A leading-edge slot leads air from near the stagnation point through a converging channel and ejects it at high speed at the low-pressure region on the upper surface . Flap (trailing-edge) slots 20 Leading-edge slot Trailing-edge slotted flap

21. 21 Plain Flaps Split Flaps Slotted Flaps Fowler Flaps Slotted Fowler Flaps

22. Slots & flaps 22

23. Racing car aerodynamics 23

24. 24

25. #1 Frontal area The frontal area of the car should be as small as possible .   25

26. #2 Front splitter The front splitter helps improve stability and cornering by increasing downforce at the front of the vehicle. 26

27. #3 Dive planes Dive planes deflect the wind upwards, pushing the front of the car down as a result. which improves grip and stability , especially during cornering. 27

28. #4 Wheel arch ventilation The front wheels rotate at a high velocity which creates a high-pressure zone inside the wheel well. 28

29. #5 Top air intake Fills the engine with undisturbed, high-speed, denser airstream. Regulates engine temperatures. Minimizes drag while optimizing airflow. 29

30. #6 Rear wing Inverted aerofoil  generates downward force. 30

31. 31 #7 Spoiler

32. 32

33. 33 #8 Rear diffuser (venturi)

34. 34 A car is said to oversteer when the rear wheels do not track behind the front wheels but slide out towards the outside of the turn. Understeer is the condition in which the front tires do not so follow the intended trajectory the driver is trying to impose while taking the corner,