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Aerodynamics in cars

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basic aerodynamic design consideration of automobile, importance of car aerodyanamic design, various aerodynamic devices use in car body,different tools require for anlysis of aerodynamic

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Aerodynamics in cars

  1. 1. AERODYNAMICS IN CARS BY, ABHISHEK T MENDHE M.Tech (Heat power)
  2. 2. INTRODUCTION CLASSIFICATION:- on basis of flow environment 1.External Aerodynamics 2. Internal Aerodynamics on basis of flow behavior 1.Subsonic 2.sonic 3.Supersonic When objects move through air, forces are generated by the relative motion between air and surfaces of the body, study of these forces generated by the motion of air is called aerodynamics.
  3. 3. FIELD OF APPLICATION:- 1.Aerospace Engineering 2.Design Of Automobile 3.Prediction of forces & moments in ships and sails 4.In design of bridges and buildings for calculating wind loads
  4. 4. Aerodynamic Forces on Aerofoil 1.Lift (causes body to rise) 2.Drag (Fluid resistance) 3.Weight 4.Thrust Considered a aerofoil move through air, forces which are considered for aerodynamic analysis over aerofoil are, Aerofoil
  5. 5. 1.Lift :- It is the sum of all fluid dynamic forces on a body normal to the direction of external flow around the body. it is caused by Bernoulli’s effect . It results body to rise by creating pressure difference . 2.Drag:- It is the sum of all external forces in the direction of fluid flow, so it acts opposite to the direction of the object. it is the force which opposes forward motion of the body through fluid. 3.Weight:- It is actually just the weight of the object that is in motion. i.e. the mass of the object multiplied by the magnitude of gravitational field. 4.Thrust:- When a body is in motion a drag force is created which opposes the forward motion of the object so thrust can be the force produce in opposite direction to drag. it must be higher than that of drag so that the body can move through the fluid.
  6. 6. ADVANTAGES OF AERODYNAMICS IN CARS It is essential that aerodynamics be taken into account during the design of cars as an improved aerodynamics in car would attain 1.More fuel efficiency 2.Higher speeds 3.Good Aesthetic and stylish appearance of car. 4.More stability of car at higher speed 5.Reduces noise level
  7. 7. History & Evolution of Aerodynamic In CarsCar design in 1920:- In the earlier times aerodynamics was not a factor as the cars where traveling at very slow speeds, but with increase of speeds it is necessarily for cars to become more streamlined, which resulted in smooth design and almost all corners of car are rounded off . during this period majority of the work was done on reducing air drag . Car design in 1950:- up to 1950 the aerodynamic drag had been cut by about 45% of the early cars. However, after this the level of drag found on cars began to slowly increase. This is due to cars were becoming more family friendly. This changes the streamed lined shape of car into rectangular shape which is more purposeful to give comfort for the family rather than reducing drag.
  8. 8. Car design 1970:- During the 1970’s there was a fuel crisis and so the demand for more economical cars became greater, which lead to changes in car aerodynamics for achieving more economical cars. If a car has poor aerodynamics then the engine has to do more work to go the same distance as a car with better aerodynamics. Hence, there is increase in demand for improved aerodynamic cars in order to be more economical for family Present design:- Now a days almost all cars are manufactured aerodynamically for having good looking, stylish and fuel efficient car.
  9. 9. STUDY OF AERODYNAMICS IN CARS 1.Drag Force:- some energy are lost to move the car through the air & this energy is used to overcome a Drag force. In vehicle aerodynamics drag is due to Frontal pressure and Rear vacuum. For calculating drag force following formula is use F = ½ CDAV² Where, F - Aerodynamic drag force A - Frontal area C - Coefficient of drag V - Velocity of object D - Density of air In order to improve the aerodynamics of cars, we must know how the flow of air past a car. the major forces which affecting the motion of car in fluid flow are, 1.Drag Force 2.Lift or Down force.
  10. 10. Coefficient of drag:- The drag coefficient is a common measure of aerodynamic efficiency in a automotive design. The drag coefficient is a unit less value that denotes how much an object resists movement through a fluid such as water or air. Hence the coefficient of drag must have low value which leads to low drag force and ultimately increases aerodyn- amic efficiency of car. Different Values of drag coefficient for various shapes body is given as,
  11. 11. FRONT END OF CAR Drag Force due to Frontal pressure:- This Drag force is caused by the air attempting to flow around the front of the car. When Air molecules approaches the front of the car they begin to compress and raise the air pressure in front of car. Frontal pressure is reduced by minimizing exposed frontal surface area and making front end smooth, continuous curve originating from the line of front bumper allowing the air molecules to pass smoothly.
  12. 12. REAR END OF CAR Drag Force due to Rear Vacuum:- Rear vacuum is caused by the Flow Detachment in the air flow as the car passes through it. Flow Detachment is inability of air molecules to fill the empty zones which are created at the rear end of vehicle. Which results in continuous vacuum zone in the opposite direction of Vehicle motion in the rear area. Drag forces are increases due to turbulence in the rear end which is caused due to flow detachment
  13. 13. To decrease drag force, it is necessary to decrease Flow detachment . It is achieved by allowing the air molecule to follow continuously the contours of a car's body. this can be ideally achieved by a long , smooth surface and gradual slope at rear end. Hence, shape of car is streamlined so that air molecule flow smoothly towards the end of car to avoid flow detachment .
  14. 14. 2.LIFT OR DOWN FORCE:- Every object traveling through air creates either a lifting or down force situation. Down force is the same as the lift experienced by airplane wings, only the difference is, it acts to press down, instead of lifting up . It is calculated as F=(1/2)CLdV2A For a given volume of air, the higher the speed of air molecules, the lower is the pressure and vice-versa This creates low pressure over hood, roof and trunk which increases the chances of rise of vehicle.
  15. 15. Overall to increase the performance of car aerodynamically. It is necessary to Generate right amount of Down Force While keeping Drag Force to a minimum level The underside of the car is also responsible for creating lift or down force. If a car's front end is lower than the rear end, then the widening gap between the underside and the road generates vacuum or low pressure area, and therefore suction is created that equates to down force.
  16. 16. AERODYNAMICS DEVICES IN CARS 1.WINGS 2.SPOILER 3.SCOOPS
  17. 17. 1.WINGS:- Probably the most popular form of aerodynamic device is the wing. Wings perform very efficiently and generating lots of down force in the car. The wings works by differentiating pressure on the top and bottom surface. Air molecules approaching the leading edge of the wings are forced to travel different distances over and below the wings. which results in lower pressure area under the wing and allows the higher pressure area above the wing to "push" down on the wing, and hence the car is stable during high speed.
  18. 18. 2.Spoiler:- They act like barriers to air flow, in order to build up higher air pressure in front of the trunk of car. It is mostly used in race cars which are lighter in rear end because low pressure created above the trunk which lifts the rear end of car. Hence spoilers are use to create high pressure that pushes down the car and also it gives stability at corners.
  19. 19. 3.Scoops:- Scoops, or positive pressure intakes consist of the air box which has an opening that permits an adequate volume of air to directly enter . Its main function is to provide high pressure, denser and adequate volume of outside air directly into the the engine compartment.
  20. 20. Aerodynamics in F1 car Aerodynamics is the single most important aspects of F1 car design, it defined the entire shape of the car
  21. 21. METHODS FOR EVALUATING AERODYNAMCIS OF CARS 1.Wind tunnel:- A wind tunnel is a research tool developed to study the effects of air moving over or around solid objects. Air is blown or sucked through a duct equipped with a viewing port and instruments. where models or geometrical shapes are mounted for study. wind tunnel testing is a trial and error process
  22. 22. 2.SOFTWARES:- Number of software’s are developed for the analysis and optimization of aerodynamics in automobiles. For the design and analyzing aerodynamics the most commonly used software’s are CATIA , HYPERMESH, ICEMCFD, FLUENT and other CFD software. software programs makes possible to test small size parts which are costly in the wind tunnel.
  23. 23. THANK YOU

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