MadSci Network: Engineering
Query:

Re: how do aerodynamics affect a car

Date: Sun Nov 14 07:19:22 1999
Posted By: Stanley F DeForest, Staff, Materials Engineering Research, Valeo Automotive
Area of science: Engineering
ID: 942192975.Eg
Message:

Aerodynamics is nothing more than changing the shape of a car to change 
how the air moves around it.  Air has mass and will resist things moving 
through it.  Ever put your had out the window of a moving car?  Did you 
ever notice that if you turn your hand sideways, the air doesn't push on 
it as much.  Basically, that's aerodynamics.  The goal of the vehicle 
designer is to minimize this effect on a vehicle.  There are a few ways to 
do this.
1) Minimize the total frontal area of the vehicle.  Obviously a dump truck 
has to push more air out of the way than a motorcycle.  
2) Make the air move more easily over the vehicle.  A vehicle that 
is 'blocky' in shape (like a jeep) won't let the air flow around it as 
easily as, say, a corvette. Also, ever see a wide piece of plastic 
sticking down under a car, up front, just before the engine?  That's 
calles an air dam and is used to deflect air away from the underside of a 
vehicle.  All the pipes, tubes, and other things under a car cause a lot 
of drag.  The goal is to get the car to move through the air rather than 
pushing it out of the way.

Engineers use wind tunnels to fine tune the body design.

The vehicle designer can also use the air to change the way the car 
performs by channeling air to cool brakes or funnel air to the radiator.  
The big 'tails' you may have seen on race cars use the air to push down on 
the rear end to give more traction (this is called downforce).  The wings 
you see on most cars on the streets are mostly for looks.
  
Having a design that is good at moving through the air is called 
being 'aerodynamically efficient'.  The same thing applies for anything 
moving through air (or water, or anything that has mass) such as ships, 
airplanes, fan blades, rockets, submarines, fish and frisbees!  Better 
efficiency means better gas milage and less power needed to move the car 
at highway speeds.




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