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People who design things that move through the air, or have air move past them need to be familiar with aerodynamics. The study of airflow and the forces involved when an object moves through the air, or when air moves past an object is called aerodynamics.

PROJECTED FRONTAL AREA

Frontal AreaThe first important thing to know about aerodynamics is “Projected Frontal Area.” As your car rolls down the track and through the air it moves air out of its way. Projected frontal area is a measurement in square units (square inches, feet, etc.) that describes how much air an object moves as it travels. Think of it as the size of the hole that your car pokes through the air as it goes.

TYPES OF AIRFLOW

There are two types of air flow that are studied in aerodynamics; laminar and turbulent. Laminar flow is when the air flowing around an object remains relatively smooth. The air flows in layers that never cross each other. In a wind tunnel sometimes tracks of smoke-like vapor are used to visualize the flow of air over an object. Where the tracks of vapor stay parallel to each other there is laminar flow.

Turbulent flow (also called turbulence) is airflow resulting from the break up of laminar flow, resulting in tumbling, swirling or violently agitated motion. In a wind tunnel using the vapor tracks, turbulence shows up when the smoke swirls or dissipates.

Turbulent flow is created when the direction of laminar air flow is changed too drastically, and/or flows past an edge or corner of an object

SEE IT IN ACTION

Wind Tunnel Sometimes when engineers use a wind tunnel they tape small lengths of ribbon at different places on the object being tested. The ribbon is taped down at the front end and left free at the other end. If the ribbon stays straight when air flows over the object, laminar flow is present at that point. If the tape flaps around wildly, then turbulent flow is present at that point. Click on the "wind tunnel" link on the right panel of this page to view a video of a model truck in a wind tunnel.

See how much turbulence there is right after the corners of the truck. Also see how design changes can be made and tested on a model in a wind tunnel to predict results on an actual vehicle.

Laminar flow, turbulent flow and projected frontal area will have an effect on forces acting on your car. Go to the next page to find out what these forces are…

   

 

FRONTAL AREA and FLOW

LIFT and DRAG

SUMMARY

WIND TUNNEL

 

 
   

 

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