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FLYING CARS
A Recipe for Aerodynamic Design
WIND NOISE is reduced by smoothing air flow This is interference drag, and might cause mirror to
around parts of the car body that tear the air to double amount of wind resistance.
create turbulence, and noise. Designer Walter Korff • High speed directional instability. Many sports
suggests these automotive body design points, as wind cars suffer from lack of directional stability at high
reducers: speed. Placing more weight on rear wheels to avoid
• Skin friction, air flow separation, and turbulence. spin only aggravates the problem. Problem can be
Windows should be flush with surface and rip mold aerodynamic, weight distribution, suspension, lack of
ing eliminated. Windshield rounded into side win frame torsional rigidity, steering, tires, or a combina
dows to avoid airflow separation caused by sharp tion of all factors. Car bodies should be designed
corners. so air forces tend to head car into wind like a
• Smooth belly-pan to reduce wind resistance. weather vane.
Various brackets, springs, axles, steering rods and Use of underpan normally is the greatest reduction
levers are real wind catchers, causing underside to in drag coefficient, says Korff. Improvements in
be major source of wind resistance. Bumpers, mirrors, internal ducting for radiator also provide a gain
door handles, fenders, headlights should be blended without sacrificing appearance. In short, low frontal
into smooth contours, eliminated or reduced as much area is half the problem of low wind resistance;
as practicable. low coefficient of drag is the other half. Interference
• Interference drag. Objects in path of curved drag should be avoided. Induced drag or lift can
airflow have more wind resistance due to relatively be a serious problem on high speed stability by re
faster airflow. A rear-vision mirror on fender near ducing tire adhesion and altering fore-and-aft balance.
side of windshield would be in curved path of faster More vertical area behind center of gravity is the
moving air around side of the windshield corner. cure, even if it is a vertical fin or fins.
Tunnel floor
This air around sides
instead of over hood
A
V
o
Endless moving belt
Wind Tunnel Ground Simulation
Techniques 111
aerodynamics still lags behind ability of funds for costly aero full performance and stability
that of aircraft and is 30-40 dynamic studies for land vehicles potential. Stability involves a
years from where aircraft is to is difficult to arrange. Wind non-linear and highly complex
day. Many drivers and designers tunnel testing is still in its in interaction between suspension,
are baffled by the term. Others fancy in developing meaningful tires, weight distribution, driver
feel aerospace technology is too ground vehicle data. inputs and aerodynamics.
sophisticated for land vehicles. Today the racing car must be Practical applications of cer
And in the belief it’s stiSl an in considered a complete system tain types of racing cars often
exact science when applied to rather than just a mechanical or outweigh the aerodynamic con
high performance cars, avail aerodynamic entity to realize its siderations. For example, on a
22 Machine Design
