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MOTORING MADE SIMPLE
Every conceivable type of transportation is affected by aerodynamics, whatever the medium. Aerodynamism helps in reducing the resistance on the vehicle and the resulting impact on fuel consumption and stability.
Perfecting the aerodynamism of cars has come into sharp focus during past few decades. With an increasing need for improvement in fuel efficiency and the changing design expectations amongst car buyers, automobile aerodynamism has become a specialized subject that carmakers fine tune to distinguish their cars from the rest in the market.
Drag Coefficient
One piece of jargon that many of us would have heard of being touted even for cars being sold in India is Coefficient of Drag or Drag Coefficient (Cd). This is an index that is used to indicate the aerodynamism of a vehicle. The Cd ranking works in the reverse order with vehicles that have a lower Cd value being the more aerodynamic compared to ones with a higher value.
The primary areas of interest while working on automotive aerodynamics are reducing drag (wind resistance), reducing the wind noise in the cabin and preventing excessive lift forces at high speed travel that could pose a threat to the stability of the vehicle. On the contrary, in the case of racing cars, aerodynamism's principles are used to enable the vehicle to produce beneficial downward aerodynamic forces to improve road-hugging traction, which in turn enahnces the racing vehicles cornering abilities, a key advantage during races.
More than half the total power required for a car to cruise at sustained speeds on the highway is taken up in overcoming the drag caused by the air hitting the vehicle. This opposing force of air increases exponentially with an increase in speed. A vehicle with a lower Cd will be better placed to allow smoother flow of air past the vehicle's front profile thereby enabling an improvement in fuel-efficiency.
To improve (lower Cd value) the aerodynamism of a vehicle, automobile designers try to integrate the front features of the such as the headlamp, bumper and bonnet panel into a smooth flowing surface. Streamlining the car/ vehicle's various features also involves avoiding abruptly flat surfaces that may jut into the slip stream that have the potential of a build up of wind resistance at higher speeds. This helps improve the fuel efficiency of the car and in keeping the cabin noise levels low.
In addition to the smoothening the flow of air over the car, improving the aerodynamism of a vehicle also involves keeping the underbody as flat and smooth as possible to get the most benefit from what is called the Venturi effect, which helps the car to produce downwards aerodynamic forces. These forces help keep the car down on the road at high speeds, when wind lift forces are usually high.
Most modern luxury cars will have a drag coefficient of amywhere between 0.28 to about 0.35. The new Mercedes Benz S-Class is said to have a low Cd value of about 0.26, as does the new Toyota Camry and the hybrid Prius.
S. MURALIDHAR
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