# Hands-on ActivityWindy Tunnel

### Quick Look

Time Required: 45 minutes

Expendable Cost/Group: US \$0.00

(Requires computers with Internet access.)

Group Size: 2

Activity Dependency: None

Subject Areas: Algebra, Physical Science

NGSS Performance Expectations:

This activity requires the resource(s):

### Summary

Through this activity, Bernoulli's principle as it relates to winged flight is demonstrated. Student pairs use computers and an online virtual wind tunnel to see the influence of camber and airfoil angle of attack on lift. Activity and math worksheets are provided.
This engineering curriculum aligns to Next Generation Science Standards (NGSS).

### Engineering Connection

As part of the iterative engineering design process, engineers continuously check and modify their designs before they achieve success and are considered final. Wind tunnels and computer simulations of wind tunnels enable aerospace engineers to test wing designs before they build full-size aircraft. By using small-size models and computer simulations, engineers can test the performance of their design in a less-expensive, efficient and safe manner.

### Learning Objectives

After this activity students, should be able to:

• Use computer software (available on the internet) to model the lift on an airplane wing.
• Explain the variables that affect lift.
• Solve linear math equations with known and unknown variables.
• Describe a real-world application of Bernoulli's principle.

### Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

###### NGSS: Next Generation Science Standards - Science
NGSS Performance Expectation

MS-PS2-2. Plan an investigation to provide evidence that the change in an object's motion depends on the sum of the forces on the object and the mass of the object. (Grades 6 - 8)

Do you agree with this alignment?

Click to view other curriculum aligned to this Performance Expectation
This activity focuses on the following Three Dimensional Learning aspects of NGSS:
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Plan an investigation individually and collaboratively, and in the design: identify independent and dependent variables and controls, what tools are needed to do the gathering, how measurements will be recorded, and how many data are needed to support a claim.

Alignment agreement:

Science knowledge is based upon logical and conceptual connections between evidence and explanations.

Alignment agreement:

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

Alignment agreement:

All positions of objects and the directions of forces and motions must be described in an arbitrarily chosen reference frame and arbitrarily chosen units of size. In order to share information with other people, these choices must also be shared.

Alignment agreement:

Explanations of stability and change in natural or designed systems can be constructed by examining the changes over time and forces at different scales.

Alignment agreement:

###### Common Core State Standards - Math
• Represent and analyze quantitative relationships between dependent and independent variables. (Grade 6) More Details

Do you agree with this alignment?

• Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities. (Grade 7) More Details

Do you agree with this alignment?

• Solve linear equations in one variable. (Grade 8) More Details

Do you agree with this alignment?

###### International Technology and Engineering Educators Association - Technology
• Students will develop an understanding of the relationships among technologies and the connections between technology and other fields of study. (Grades K - 12) More Details

Do you agree with this alignment?

###### State Standards
• Represent and analyze quantitative relationships between dependent and independent variables. (Grade 6) More Details

Do you agree with this alignment?

• Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities. (Grade 7) More Details

Do you agree with this alignment?

• Solve linear equations in one variable. (Grade 8) More Details

Do you agree with this alignment?

• Predict and evaluate the movement of an object by examining the forces applied to it (Grade 8) More Details

Do you agree with this alignment?

• Use mathematical expressions to describe the movement of an object (Grade 8) More Details

Do you agree with this alignment?

Suggest an alignment not listed above

### Materials List

Each group needs:

### Introduction/Motivation

If you arm wrestle someone---who wins? Well of course, the person who exerts the most force wins! But, if both "wrestlers" push with the same force, their arms do not move. Lift on airplane wings is somewhat similar. As air flows over the top and bottom of the wing the pressure and velocity of the air change. These changes create lift. But on a symmetric wing, the changes on the top half match the bottom half. If the forces on the top and bottom of the wing are the same, no lift results. Because the cambered airfoil (the curve in the wing) is not symmetric, the forces on the top and bottom are different—in this case, lift is generated.

Can you ever have lift on a symmetric airfoil? Yes, if you raised the nose of the airplane. Doing this places the wing at an angle. Engineers call this the angle of attack. Now the forces on the top and bottom of the wing are different, and create lift.

The greater the angle of attack, the more lift; however, this only works up to a certain angle. If the angle is too high, the air will not flow smoothly over the airfoil and no lift can be created; in this case, the wing stalls, which means it loses lift.

Engineers often use wind tunnels to see how the air is flowing and if it flows smoothly over a wing. They do this by filling a wind tunnel's air chamber with smoke and watching as the (smoky) air blows over a model wing. This process also helps them determine how much drag an airfoil has by the size of the wake (an area where the airflow is not smooth at the trailing edge of the airfoil). They can also observe stall when the air has separated from the wing and starts to flow towards the front of the airfoil.

Now try out the virtual wind tunnel yourself!

### Procedure

Background on Wind Tunnels

If you were to slice apart a wing from its leading (front) edge to its trailing edge (back), the "cutaway" illustrated in the Figure 1 is what you would see. Aeronautical engineers call this an airfoil.

The top and bottom halves of the first airfoil are identical—this is referred to as symmetric. The airfoil on the right is not symmetric: its top and bottom halves are different. The difference in the bottom from the top means this airfoil is cambered.

Four Forces of Flight

The four forces of flight are lift, weight, thrust and drag. Lift and weight are opposites and counteract one another. Likewise, thrust and drag counteract each another.

How Does the Bernoulli Principle Create Lift?

The top of a plane's wing is longer than the bottom because it is curved (see Figure 2). This means air travels faster over the top of the wing than under it. As a result, the air moving over the top has less time to push on the wing, creating less air pressure than air passing below the wing. In Figure 2, the air moving under the wing moves slower and exerts more pressure/force on the wing than does the air moving over the wing. Since more force exists under the wing than above it, the net result is that the wing rises up, creating lift. This principle forms the basis of winged flight.

Flaps are located the front and back edges of airplane wings. During takeoff and landing, pilots extend the flaps on the back edge of the wing. The flaps increase the curve of the wing, which maintain the lift at slower speeds. After takeoff, the pilot retracts (puts back in) the flaps. Engineers continuously test their airplane wing designs to determine the lift, and in so doing, they consider the following:

• The amount of air diverted by the wing is proportional to the speed of the wing and the air density.
• The vertical velocity of the diverted air is proportional to the speed of the wing and the angle of attack.
• The lift is proportional to the amount of air diverted times the vertical velocity of the air.
• The power needed for lift is proportional to the lift times the vertical velocity of the air.

Before the Activity

• Make copies of the worksheets.
• Bring up on the computers the virtual wind tunnel website at: http://wayback.archive.org/web/20120502104554/http://www.swe.org/iac/LP/wind_tunnel.html. UPDATE: Since this activity was first published, its online virtual wind tunnel resource (by Society of Women Engineers, swe.org) has gone away. It can, however, still be accessed via the Internet Archive Wayback Machine at http://wayback.archive.org/web/20120524022956/http://www.swe.org/iac/LP/wind_tunnel.html.

With the Students

1. Discuss Bernoulli's principle and introduce the concept of lift, as provided in the Introduction/Motivation and Background sections.
2. Explain the difference between a symmetric and cambered (asymmetric) airplane wing.
3. Direct students' attention to Worksheet 1 and the virtual wind tunnel website . Have students read the background information silently to themselves. After 10 minutes, discuss the reading as a class.
4. Divide the class into student pairs.
5. Be sure to model the process. Students may find it difficult to grasp how the model runs. The model depicts velocity lines flowing over different wing types. Velocity lines that are close together above the wing demonstrate lift; lines that are the same distance apart above and below the wing demonstrate no lift.

Instructions for Virtual Wind Tunnel

1. Pick an Airfoil Shape from column #1.
2. Pick an Angle of Attack from column #2.
3. Click "Run Tunnel."
4. Close the window when you are done with this activity.
5. Have students complete the worksheet. Be sure they try several models to decide which causes the most or least lift.
6. Be sure to model the process. Students may find it difficult to turn the English sentences into math equations. The worksheet walks students through the process step-by-step.
7. Discuss with students that the phrase "proportional to something " means "equal to some number multiplied by something." More specifically, we can say "is proportional to" means K times something where K is the constant of proportionality.
8. Assign Math Worksheet 2 for students to complete as homework. (The worksheet may be too difficult lower grades.)

### Assessment

Pre-Activity Assessment

Discussion Question/Answer: Ask students questions and have them raise their hands to respond. Write their answers on the board

• If you arm wrestle someone, who wins? (Well of course, the person who exerts the most force wins!)
• What happens if both "wrestlers" push with the same force? (Their arms do not move.)
• How does this relate to lift? (Lift occurs when the force under a plane is greater than the force pushing down on the plane [weight]. This is similar to arm wrestling since the person who exerts the most force pushes the other arm in that direction.)
• Describe the force of lift and how it affects airplane flight. (Expect that students understand Bernoulli's Principle and can explain that lift is caused when air is pushing harder from below a wing than from above a wing.)

Activity Embedded Assessment

Worksheet 1: Have the students record their activitiy observations and comments on their Worksheet 1: Virtual Windy Tunnel. After students have finished their worksheets, have them compare answers with their peers. Then discuss as a class.

Post-Activity Assessment

Worksheet 2: Assign students to complete Math Worksheet 2: Windy Tunnel: What Does It Mean? as homework. Review their answers to gauge their comprehension of the subject.

Figure Drawing/Race: Draw an airfoil on the classroom board or overhead projector (see Figure 1 for example airfoils). Have two students come to the board and race who can draw the top or the bottom of the airfoil the fastest. The student who "wins" completes the drawing (gets to the end of the airfoil) first. Which student was the fastest? Will that airfoil create lift or not?

### Troubleshooting Tips

• Make sure students understand the instructions.
• Make sure all computers are open to the virtual wind tunnel website.
• Be sure to have students read the background information or review it as a class.

### Activity Extensions

A great teacher demo on lift is to throw a Frisbee. The shape of the top of the Frisbee is smooth and air flows over the top faster, creating less pressure. It takes longer for air to flow over the bottom of a Frisbee, thus creating a higher-pressure area that lifts the Frisbee up into the air.

Have students compare airfoil shapes with the wing shapes on different airplanes. Why do different planes have different wing shapes?

Have students research the work of aerospace engineers and how they use lift/drag in their designs.

### Activity Scaling

For lower grades: Read the wind tunnel instructions together, ask a class, and ask for questions after they have been read. While the math worksheet may be too difficult, you can walk through the steps of creating a math equation as a class.

### Subscribe

Get the inside scoop on all things TeachEngineering such as new site features, curriculum updates, video releases, and more by signing up for our newsletter!
PS: We do not share personal information or emails with anyone.

### More Curriculum Like This

Upper Elementary Lesson
May the Force Be with You: Lift

Students revisit Bernoulli's principle (presented in lesson 1 of the Airplanes unit) and learn how engineers use this principle to design airplane wings. Airplane wings create lift by changing the pressure of the air around them. This is the first of four lessons exploring the four key forces in fli...

Middle School Lesson
Can You Take the Pressure?

Students are introduced to the concept of air pressure. They explore how air pressure creates force on an object. They study the relationship between air pressure and the velocity of moving air.

### References

This activity was adapted from the “Wings in a Wind Tunnel” activity at the Society of Women Engineer's Internet Activity Center at http://www.swe.org/iac/LP/wind_01.html

### Contributors

Tom Rutkowski; Alex Conner; Geoffrey Hill; Malinda Schaefer Zarske; Janet Yowell

### Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

### Acknowledgements

The contents of this digital library curriculum were developed under grants from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and the National Science Foundation (GK-12 grant no. 0338326). However, these contents do not necessarily represent the policies of the DOE or NSF, and you should not assume endorsement by the federal government.