Drag reduction methods in Cars

What does drag to your car?

                     Aerodynamic drag is one of the main obstacles to accelerate a solid body when                   it moves in the air. About 50 to 60% of total fuel energy is lost only to overcome this                           adverse aerodynamic force.
                             
                                   
Benefits of reducing drag

1. Improves fuel efficiency
2. Improves acceleration
3. Increases maximum speed limit

Methods of Reducing Drag:

1. VORTEX GENERATOR
   
   A vortex generator (VG) is an aerodynamic device, consisting of a small vane usually attached to a lifting surface  such as an aircraft wing or a rotor blade of a wind turbine. These are also attached to some parts of cars. When the airfoil or the body is in motion relative to the air, the VG creates a vortex, which by removing some part of the slow-moving boundary layer in contact with the airfoil surface, delays local flow separation and aerodynamic stalling, thereby improving the effectiveness of wings and control surfaces.

   

   Removal of slow moving air by Vortex Generator

2. DIFFUSER  
   
   A diffuser, in an automotive context, is a shaped section of the car underbody which improves the car's aerodynamic properties by enhancing the transition between the high velocity airflow underneath the car and the much slower freestream airflow of the ambient atmosphere. It works by providing a space for the underbody airflow to decelerate and expand (in area, density remains constant at the speeds that cars travel) so that it does not cause excessive flow separation and drag, pressure recovery. The diffuser itself accelerates the flow in front of it, which helps generate downforce. The angle of difusser must be 7 to 10 degrees for best results.
   
3. REAR FAIRING

   

   Vintage Car with Rear Firing

   A fastback is a car body style whose roofline slopes continuously down at the back. It is a form of back for an automobile body consisting of a single convex curve from the top to the rear bumper.Fastbacks provide an advantage in developing aerodynamic vehicles with a low drag coefficient. This is due to the attached boundary layer on the rear end of the car. Due to separation in the boundary layer, after the roof additional drag is contributed by the separation.

   

   Test of air flow over a modern with Rear Fairing 

4. STREAMLINED BODY    A body is said to be streamlined if a conscious effort is made to align its shape with the anticipated streamlines in the flow. y it is much easier to force a streamlined body through a fluid, and thus streamlining has been of great importance in the design of vehicles and airplanes. Streamlining was the major contribution in drag reduction of a car body. In the 1990s which revolutionized the era of automotive aerodynamics by using streamlined designs.

   

   Due to streamline design drag coefficient Cd=0.25

   

   Due to streamline design drag coefficient Cd=0.32

WHY DO WE NEED TO REDUCE DRAG?

The purpose of fluid mechanics in cars is to make the vehicle more environmentally friendly. The energy efficiency of a car is affected by a variety of factors, including size, aerodynamics, weight, and the rolling resistance of the wheels. Engineers must know all about these factors to design better cars for the future.