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    Wind Tunnel & Bernoulli’s Principle Experiments
    For Science Labs, Lesson Plans, Class Activities & Science Fair Projects
    For High School Students and Teachers







    Wind Tunnel & Bernoulli’s Principle Experiments
    This experiment is courtesy of 

    See also Wind Tunnel Experiments and Projects

    Investigating the Aerodynamics of Flight

    Developers:

    Michael B. Marchiondo, M.A. Mario Mirabelli, Ph.D.

    Valley Forge Middle School Monomers Research

    Wayne, PA Rohm & Haas Co.

     

    Grade Level:

    7 through 9;

    10 through 12 as adapted.

     

    Discipline:

    Physics, Aviation, Mathematics, Art.

     

    Goals:

    Upon completion of these lessons the student will:

    1. develop an understanding of the scientific method of inquiry.
    2. collect and analyze quantitative data.
    3. learn to incorporate quick sketching as a form of data collection
    4. learn to practice safety precautions in scientific experimentation.
    5. develop an understanding of how instrumentation is designed and utilized in research.
    6. have a conceptual foundation of the aerodynamics of flight.
    7. be aware of some applications of science in everyday life.
    8. be reinforced of the fact that learning science is fun.
    9. be encouraged to share and discuss science learning with family and friends.

     

    Introduction:

    The airways of aviation support hundreds of thousands of jobs and transport hundreds of millions of people globally every day. These numbers will continue to increase as the future becomes the present. Atmospheric flight is also the beginning and ending of every humanned space flight mission. Most students express an interest level in flying that is greater than their understanding level of the fundamental concepts involved. One of these concepts, airflow, is better learned and more thoroughly understood when seen and observed repeatedly. The experiment to build a mini wind tunnel was intended to create that airflow visualization and to conduct small scale airfoil section testing. The mini wind tunnel includes the capability to interface using computer technology with additional force sensors, interface box, software and computer, for high school adaptations.

    The following lesson plans were developed with the understanding that not everyone can choose to build this or any wind tunnel. Investigations 1, 2 and 3F can be conducted without the wind tunnel. And, although Investigations 3G and 4 require a wind tunnel, these were designed without the force probes to reduce construction cost and minimize equipment needed in the middle level classroom. The design for the wind tunnel constructed for this project was obtained from the NASA website and adapted for use.

     

     

    Investigation 1: Turning Bernoulli-Blue-in-the-Face

    Objectives:

    Upon completion of this lesson the student will be able to:

    1. create and observe the effects of Bernoulli’s Principle.
    2. better understand how Bernoulli’s Principle is related to flight.

     

    Background:

    To understand the basic principle of bird and plane flight leads directly to Bernoulli’s Principle. Daniel Bernouilli was a Swiss scientist of the eighteenth century. As Bernoulli studied the relationship between fluid speed and pressure, like why the speed of a brook increases when it flows through narrower places, he reasoned that the extra speed is acquired through a reduction of internal fluid pressure. Bernoulli’s Principle states that for fluids in steady (streamline) flow fluid pressure decreases as the speed of the fluid increases. When flight occurs, airflow above a bird’s or plane’s wing is greater than below creating a net upward force (lift) due to the higher air pressure below the wing.

     

    Suggested Time:

    1-2 class periods. It is recommended that students have prior knowledge of the fact that air is a fluid and exerts pressure.

     

    Materials/Team of 2-3:

    30cm string- 2 pieces, 2 ping -pong balls, tape, straw, ring stand with ring, thread spool, straight pin, 5cm square index card, 12cm x 20cm index card, 7cm x 21cm paper strip-3 pieces.

    CAUTION:

    EXCESSIVE EXHALING CAN CAUSE FAINTNESS OR FATIGUE IN PERSONS WITH BREATHING/RESPIRATORY DISORDERS.

     

    Student Procedures:

    Experiment A

    1. Explain on paper in 5 minutes your perspective on how birds and planes fly up.
    2. Tape each piece of string securely to a point on each ping -pong ball.
    3. Tie the ends of each string directly opposite each other on the ring of a ring stand.
    4. Measure the distance between the balls in cm.
    5. Hypothesize the behavior of the balls if you were to blow between them with a straw.
    6. Place a straw equally between the balls 2-3cm in front of them.
    7. While blowing through the straw have someone measure the distance between the balls.
    8. Draw a quick sketch of step 6 and describe results.

     

    Experiment B

    1. Crease the 12cm x 20cm index card at 90o 4cm in from each long edge to form a squashed ‘U’ shape.
    2. Set card on folded edges to form a low tunnel on the table. Record height from table.
    3. Estimate how many tries you need to blow the tunnel over.
    4. Hypothesize the behavior of the tunnel if you were to blow under it.
    5. Blow under tunnel to blow it over while someone records height from table. Record number of tries needed to blow over tunnel.
    6. Draw a quick sketch of steps 2 & 5 and describe results.

     

    Experiment C

    1. Connect the opposite corners of the 5cm square card with diagonal lines.
    2. Insert the straight pin through the crossing point on the card then into the spool’s top center hole.
    3. Hypothesize the card’s behavior if you were to blow, upward through the bottom opening.
    4. Estimate how many tries you need to blow card off of spool.
    5. Holding spool and card vertically above your head blow through the bottom center hole of spool. Record the number of tries needed to blow off the card.
    6. Draw a quick sketch of step 5 and describe results.

     

    Experiment D

    1. Place one of the paper strips between both your index finger and the curve of your lower lip.
    2. Hypothesize the paper’s behavior if you were to blow straight over it.
    3. Blow straight out over the paper.
    4. Draw a quick sketch of steps 2 & 3 and describe results.
    5. Tape the ends of the paper together to form a "wing loop".
    6. Hypothesize the loop’s behavior if you were to blow across the top of it.
    7. Insert a pencil through loop; hold to your lips and blow across the top of the wing.
    8. Draw a quick sketch of step 7 and describe results.

     

    INVESTIGATION 1: DATA COLLECTION

    EXPERIMENT

    HYPOTHESIS FIRST MEASURE
    (ESTIMATE)
    FINAL MEASURE OR COUNT

    A

         

    B

         

    C

         

    D

         

    E

         

     

     

    Conclusion Questions:

    1. How would you explain the difference in distance in Experiment A?
    2. What explanation can you develop for Experiments B & C?
    3. How do you explain the paper strip’s and wing loop’s behavior?
    4. Label all quick sketches with areas of higher and lower pressure and use arrows to show areas of increased velocity.
    5. How could you demonstrate Bernoulli’s Principle with 2 strips of paper from Experiment D?
    6. What occurs when a tractor-trailer passes you closely on the interstate?
    7. Why would ships at sea have a minimum passing distance between them?

     

    Family Funstuff:

    Let each family member use a straw to drink from at dinner. Halfway through the meal entertain a discussion of what actually occurs when one drinks through a straw and how Bernoulli’s Principle is involved.

     

     

    Investigation 2: Winging It

    Objectives:

    Upon completion of this lesson the student will be able to:

    1. define the lift, weight, thrust and drag forces acting on an airplane.
    2. identify basic plane parts.
    3. identify key features of an airfoil.
    4. determine and sketch the chord line on airfoil schematics.
    5. calculate and draw the aerodynamic center on an airfoil schematic.
    6. define camber of an airfoil.

     

    Background:

    The four fundamental forces of flight include:

    • total weight = empty plane + payload + fuel, all being pulled down by gravity;
    • lift = the upward force produced - is opposite weight;
    • thrust = the force producing accelerated forward motion;
    • drag = resistance force to forward motion; is opposite thrust

    Lift is produced by the imbalance of higher air pressure below the wing and lower air pressure above the wing, which is created by the increased airflow over the wing from the forward thrust of the engines. When lift equals weight and thrust is greater than drag, horizontal flight is possible. The amount of lift a wing can generate depends on the relative airspeed, angle of attack, airfoil camber, wing geometry and wing area.

    The cross-sectional area of a wing parallel to the wing’s centerline and perpendicular to the wing horizon is called the airfoil. The chord is the line connecting the leading and trailing edges through the airfoil. Upper and lower camber refer to the curvature lengths measured from the leading to trailing edges of the airfoil above and below the chord line, respectively. The angle of attack is the intersection between the relative wind direction (not necessarily horizontal) and the chord line. An angle of attack greater than 160 generally creates stall conditions in most airplanes (where airflow does not reattach behind the wing). Most of a plane’s lift is focused at the aerodynamic center of the wing, which is located at .25 chord length from the leading edge. Lift is greater for higher speeds and larger surface areas.

     

    Suggested Time:

    2 class periods.

     

    Materials/Student:

    Background information (above), blank plane diagram, blank airfoil diagram, airfoil NACA 0009 template, airfoil NACA 2412 template, protractor with metric ruler, 30cm of string

     

    Materials/Team of 4-5:

    labeled plane model

     

    Student Procedure:

    Activity E

    1. Use the background information and plane model to label your plane diagram with the basic parts and the fundamental forces of flight with directional arrows.
    2. Use the background information and the sample airfoil diagram to label the key airfoil features.
    3. Draw and measure in cm the chord line on the 0009 and 2412 airfoil templates.
    4. Calculate and mark the aerodynamic center of the 0009 and 2412 airfoil templates.
    5. Use the string and ruler to measure the upper and lower camber of each airfoil.
    6. Use the protractor to determine the angle of attack for the airfoil templates if the relative wind direction is horizontal.

     

    Conclusion Questions:

    1. In which part of a plane are passengers flown?
    2. Which part of the plane generates the most lift?
    3. What is the chord length of each airfoil?
    4. What is the angle of attack for each airfoil?
    5. How do the upper and lower cambers of each airfoil compare?

     

    Simulation:

    1. Use student pairs to represent symmetrical and asymmetrical airfoils, respectively.
    2. For symmetrical airfoil, start student pair at point A, have them walk different paths of equal distance to arrive at Point B simultaneously.
    3. For asymmetrical airfoil, start student pair at point A, have them walk different paths of unequal distance to arrive at Point B simultaneously.
    4. Use simulation results to compare symmetrical to asymmetrical airflow.

     

    Family Funstuff:

    Use the templates to construct an airfoil section that is 14cm wide.

     

    INVESTIGATIONS 3 & 4 DATA CHART

    Airfoil geometry

    Attack Angle (O)

    Lift V1 (mm)

    Drag V1 (mm)

    Air Flow V1

    Lift V2 (mm)

    Drag V2 (mm)

    Air Flow V2

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    Investigation 3:Double Tunnel Vision

     

    Objectives:

    Upon completion of this lesson the student will be able to:

    1. define, identify and sketch streamline and turbulent fluid flow.
    2. identify basic wind tunnel parts and uses.

     

    Background:

    In steady fluid flow the fluid moves in streamlines, smooth paths of steady flow shaped by the boundaries of the flow (solids). The streamlines show lines of motion, indicating greater velocity as they get closer together. When streamlines pass an obstruction some may curl into eddies or vortices while most reconnect behind the obstruction to continue steady flow. If the velocity of the fluid becomes too great the streamlines disappear into turbulence or random motion (as in a plane stall) at which point the proportional relationship between pressure and fluid flow breaks down. Bernoulli’s Principle applies only to fluids in steady flow. Streamline and turbulent flow are best understood when studied visually. Using a homemade wind tunnel (construction plans in Appendix A) students can easily identify both flow types which ultimately aid in better understanding Bernoulli’s Principle and aerodynamic lift.

    A wind tunnel is a device for testing and measuring air flow pressures, forces, velocities (etc.) on static objects such bridges, buildings and monuments as well as dynamic objects such as cars, planes and spacecraft. The basic principle is to straighten and constrict airflow (settling chamber and entrance cone, respectively) to increase air velocity while creating an area of streamline flow (test section). The air is allowed to gradually expand (diffusion cone) to the exit diameter of the drive section, which draws the air through from the entrance cone.

     

    Suggested Time:

    1-2 class periods.

     

    Experiment F Materials/team of 2-4:

    sink with faucet, tablespoon

     

    Experiment G Materials/Student:

    airfoil NACA 0009 template (2), airfoil NACA 2412 template (2)

     

    Experiment G Materials/Class:

    wind tunnel, protractor transparency, water soluble fine-tip marker- 2 colors, airfoil NACA 0009 test section, airfoil NACA 2412 test section, smoke/vapor source*

    *Special Note of Caution:

    Both sources have their complications.

    30-second smoke generators (from Superior Signal Co., Spotsville, N.J.) have been tried in a modified bee smoker with adequate success outdoors. Ventilation and health risks are concerns.

    Dry ice and water have been tried with some success indoors. The vapor cloud is hard to sustain and much dry ice and water are needed.

    Although preferred in theory, liquid nitrogen with ice has not yet been tried. This would require minimal amounts, greatly reduce most concerns and equipment, be the easiest to control/sustain and could be tested indoors.

    CAUTION:

    ALWAYS PERFORM SMOKE TESTS IN WELL- VENTILATED AREAS TO PREVENT EYE AND RESPIRATORY DISCOMFORT, AND PROVIDE SAFE VIEWING CONDITIONS. USE PROPER EYE PROTECTION. HAVE FIRE EXTINGUISHER READILY AVAILABLE.

    DRY ICE AND LIQUID NITROGEN ARE EXTREMELY COLD- USE PROPER THERMAL PROTECTION FOR HANDS AND PROVIDE SAFE VIEWING CONDITIONS.

     

    Student Procedures:

    Experiment F

    1. Hypothesize the behavior of the water stream on the back curve of the spoon.
    2. With faucet on to medium flow, hold spoon by the handle and slowly move the upper curved back of spoon into the water stream. Quick sketch and describe results.
    3. With spoon still in stream slowly tilt concave upward about 100. Quick sketch and describe results.
    4. Repeat step 3 three times.

     

    Experiment G

    1. Use the background information to label a wind tunnel diagram.
    2. Observe a teacher-demonstrated smoke/vapor test with the wind tunnel on and the test chamber empty. Quick sketch and describe results.
    3. With airfoil NACA 0009 section mounted at 0o in the test chamber mark the leading edge of the airfoil on the outside of the chamber. With wind tunnel on again mark the leading edge of the airfoil with the same color. Observe a teacher-demonstrated smoke/vapor test over the airfoil. Quick sketch and or describe results.
    4. Repeat step 2 with airfoil mounted at 30o. (Use protractor transparency).
    5. Repeat steps 2 & 3 with airfoil NACA 2412 section mounted in test chamber using a different color marker.
    6. Using the airfoil templates sketch streamline schematics for both air foils at both angles.
    7. Research (Internet, if possible) where and why wind tunnels are used.
    8. Review airfoil airflow using reference streamline photos.

     

    Conclusion Questions:

    1. What does the water flow over the spoon represent?
    2. What happens to the water flow when the spoon is turned to too high an angle? What angle would this represent in mechanical flight?
    3. How are the streamlines of both airfoils similar at 0o?
    4. How do the streamlines of both airfoils change from 0o to 30o? What would you predict that a plane would do when experiencing these streamlines?

     

    Family Funstuff:

    1. While driving on a country road at 50mph place your hand horizontally palm down just out the window.
    2. Repeat step 1 slightly tilting your palm upward. Repeat several times.
    3. With your hand horizontally palm down again rotate it 90o palm outward.

     

    Questions:

    1. Which hand orientation creates the most lift?
    2. What occurs when your angle of attack is too steep?

     

     

    Investigation 4: The Wind Beneath Its Wings

     

    Objectives:

    Upon completion of this lesson the student will be able to:

    1. relatively measure airfoil movement.
    2. compare wing geometry (shape) to relative lift and drag produced.
    3. compare the angle of attack (to 20o) to relative lift produced.
    4. correlate streamline continuity to horizontal flight.
    5. reinforce Bernoulli’s Principle and streamline flow observation.

     

    Background:

    See Investigation 3 Background.

    Wind tunnels are used by Boeing, NASA, the U.S. Navy, and other industries and organizations to continually test new airfoil designs and atmospheric conditions, and compare their results to predicted theory. Using a small-scale wind tunnel with model airfoil sections allows students to conduct real world research in the classroom.

     

    Materials/Student:

    Investigation 4 data chart, 1cm graph paper- 2 sheets.

     

    Materials/Class:

    wind tunnel, airfoil NACA 0009 section, airfoil NACA 2412 section, protractor transparency, metric ruler, 5mm graph grid transparency, water soluble marker, smoke/vapor source*

    *Note:

    See *Special Note of Caution from Investigation 3.

    CAUTION:

    ALWAYS PERFORM SMOKE TESTS IN WELL-VENTILATED AREAS TO PREVENT EYE AND RESPIRATORY DISCOMFORT, AND PROVIDE SAFE VIEWING CONDITIONS AWAY FROM SMOKE SOURCE AND EXHAUST. USE PROTECTIVE EYE WEAR. HAVE FIRE EXTINGUISHER READILY AVAILABLE.

    DRY ICE AND LIQUID NITROGEN ARE EXTREMELY COLD - USE PROPER THERMAL PROTECTION FOR HANDS AND PROVIDE SAFE VIEWING CONDITIONS AWAY FROM VAPOR SOURCE AND EXHAUST.

     

    Suggested Time:

    1 - 2 class periods.

     

    Student Procedure:

    Experiment I

    1. With airfoil NACA 0009 section mounted at -10o in the test chamber mark the leading edge outside the chamber opposite Investigation 3.
    2. Secure transparent graph grid onto outside of test chamber opposite Investigation 3, aligning the axes to the chamber and one origin over the leading edge mark.
    3. Observe a teacher-demonstrated smoke/vapor test at reduced fan speed (one half or two thirds). Record the type of airflow and again mark the leading edge.
    4. Repeat step 2 with fan at full speed.
    5. Using the graph grid transparency measure in mm the vertical lift distance and horizontal drag distance for each speed.
    6. Wipe clean the leading edge marks of the two speed tests, leaving the original.
    7. Repeat steps 1 through 4 for each angle of attack, 5o, 10o, 15o, and 20o.
    8. Measure in mm the vertical lift distance and horizontal drag distance from the full speed, 0o angle of attack test in Investigation 3.
    9. Repeat steps 1 through 7 with airfoil NACA 2412 section.
    10. Construct a linear graph of angle of attack vs. lift in mm showing both airfoils.
    11. Construct a linear graph of speed vs. lift for each speed for both airfoils.

     

    Conclusions-Questions:

    1. What is the angle of attack range that displays streamline continuity?
    2. Which airfoil generates greater lift and why?
    3. Which airfoil produced the greatest amount of drag and why?
    4. What is the relationship between relative air speed and lift?
    5. What is the relationship between angle of attack and lift?
    6. Using models & photographs, compare and contrast the wings of a glider to that of a jet fighter.

     

    Family Funstuff:

    Enlist parents or community resource personnel in the aviation and piloting industries to guest speak to your class or team. Visit an air (& space) museum. Tour a small local airport, traffic control tower &/or wind tunnel facility.

     

    Partnership Potential:

    One high school application suggestion would be the development of a partnership amongst the art, science and technology education departments. Tech Ed could create construction teams responsible for different sections of the wind tunnel and final assembly. Art could create engineering teams to design and make airfoil sections to be tested in the wind tunnel by flight teams in science.

     

    Charts and Diagrams

    • first
    • second
    • third
    • fourth
    • fifth

     

    Bibliography:

    • American Institute of Aeronautics and Astronautics. Mini Wind Tunnel. http://home.earthlink.net/~fosters/wt.html#desc
    • Cevalier, Howard L. Model Aircraft Design and Performance for the Modeler. Challenge Engineering, Inc. New Baden, 1993.
    • Herbert, Don. Mr. Wizard’s Science Secrets. Popular Mechanics Co. USA, 1952.
    • Hewitt, Paul G. Conceptual Physics. Little, Brown & Co. Boston, 1985.
    • Rogers, Eric M. Physics for the Inquiring Mind. Princeton University Press. Princeton, 1960.
    • Simons, Martin. Model Aircraft Aerodynamics. Argus Books, Biddles Ltd. Great Britain, 1994.
    • The Baals Wind Tunnel. http://ldaps.ivv.nasa.gov/Curriculum/tunnel.html

     

    Web Sites to Surf:

    This experiment is courtesy of 



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