Make Your Own Wind Tunnel
Make Your Own Wind Tunnel
Materials
* 3-4 medium-sized cardboard boxes
* duct tape
* small- to medium-sized scale to measure weight
* variable-speed fan
Make a wind tunnel out of several boxes taped together with both ends open. The wind tunnel should be large enough that both hands will fit into it easily. Before taping the tunnel together, make one-inch divisions on the floor of the tunnel for measuring the distance that objects move when the wind current is applied. Have the students determine the ratio of the weight of the object (using a scale) to the distance it moves (in inches) when the fan is turned on. You can also have the students turn on the fan at different speeds to make a mathematical comparison between the force of the air and the distance the object moves.
Ideas for objects in the tunnel: pencil, paper clip, tissue, cotton, small- to medium-sized balls, barrette, bottle cap.
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Questions for Discussion
Q: Can you think of other sources of airflow that could be used to test airfoils?
A: Wind-swept ridges and blowing cave mouths could be used to test airfoils. Before building their own wind tunnel, the Wright brothers employed an unconventional testing machine: a bicycle with a third wheel mounted horizontally on the front of the frame. Two test shapes were mounted on the wheel, and the bicycle was pedaled rapidly (up to 15 mph) up and down the streets of Dayton, Ohio. The airfoil being tested would produce a torque in one direction, but this was counterbalanced by an opposite torque from a reference shape. The rotating balance was brought into equilibrium by changing the airfoil's angle of attack.
Q: What are some of the advantages of wind tunnels?
A: Advantages of wind tunnels include reliable and consistent airflow, low turbulence, ability to make precise measurements, and reproducible conditions and results.
Q: What kinds of things can benefit from wind tunnel testing?
A: Aircraft, spacecraft, rockets, cars, trucks (reduced aerodynamic drag reduces fuel costs for long-distance truckers and increases top speeds of racecars), and buildings (to help quantify stresses from high winds) can be tested in wind tunnels.
Q: How does air flowing over a surface create lift?
A: Most wings are shaped so that air must flow faster over the top than the bottom. This results in a lower pressure on the top of the wing than on the bottom, and creates lift (Bernoulli lift).
Dynamic lift is caused by the pressure of impact air against the lower surface of the airfoil. This is what you feel when you put your hand, angled upward, out the window of a moving car.(*We suggest that you not stick your hand out of a moving car.)
Materials
* 3-4 medium-sized cardboard boxes
* duct tape
* small- to medium-sized scale to measure weight
* variable-speed fan
Make a wind tunnel out of several boxes taped together with both ends open. The wind tunnel should be large enough that both hands will fit into it easily. Before taping the tunnel together, make one-inch divisions on the floor of the tunnel for measuring the distance that objects move when the wind current is applied. Have the students determine the ratio of the weight of the object (using a scale) to the distance it moves (in inches) when the fan is turned on. You can also have the students turn on the fan at different speeds to make a mathematical comparison between the force of the air and the distance the object moves.
Ideas for objects in the tunnel: pencil, paper clip, tissue, cotton, small- to medium-sized balls, barrette, bottle cap.
Back to top
Questions for Discussion
Q: Can you think of other sources of airflow that could be used to test airfoils?
A: Wind-swept ridges and blowing cave mouths could be used to test airfoils. Before building their own wind tunnel, the Wright brothers employed an unconventional testing machine: a bicycle with a third wheel mounted horizontally on the front of the frame. Two test shapes were mounted on the wheel, and the bicycle was pedaled rapidly (up to 15 mph) up and down the streets of Dayton, Ohio. The airfoil being tested would produce a torque in one direction, but this was counterbalanced by an opposite torque from a reference shape. The rotating balance was brought into equilibrium by changing the airfoil's angle of attack.
Q: What are some of the advantages of wind tunnels?
A: Advantages of wind tunnels include reliable and consistent airflow, low turbulence, ability to make precise measurements, and reproducible conditions and results.
Q: What kinds of things can benefit from wind tunnel testing?
A: Aircraft, spacecraft, rockets, cars, trucks (reduced aerodynamic drag reduces fuel costs for long-distance truckers and increases top speeds of racecars), and buildings (to help quantify stresses from high winds) can be tested in wind tunnels.
Q: How does air flowing over a surface create lift?
A: Most wings are shaped so that air must flow faster over the top than the bottom. This results in a lower pressure on the top of the wing than on the bottom, and creates lift (Bernoulli lift).
Dynamic lift is caused by the pressure of impact air against the lower surface of the airfoil. This is what you feel when you put your hand, angled upward, out the window of a moving car.(*We suggest that you not stick your hand out of a moving car.)
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