Winglets in Wind Tunnels
Abstract
Winglets are the short vertical "fins" at the wingtips of some airplanes. Have you ever wondered why they are there? If you have access to a wind tunnel, you can build model airfoils with and without winglets and see for yourself. If you're really ambitious, you can also build your own wind tunnel.Objective
The goal of this project is to measure the changes in airfoil performance when winglets are added to the airfoil.
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Credits
Andrew Olson, Ph.D., Science Buddies
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Last edit date: 2018-03-03
Introduction
The Boeing jet in the picture at right has winglets at the tips of its wings. Why are they there? What do they do?
As an airplane moves through the air, the wings generate lift by creating an area of low pressure above the upper surface of the wing. The higher air pressure beneath the lower surface of the wing lifts the plane. At the tip of the wing, the high and low pressure air meet.
The air forms miniature tornadoes, called wing tip vortices that spread out behind the plane (see Figure 1, right). Wing tip vortices cause two problems:
- the turbulent airflow they create can be strong enough to flip an airplane that encounters it;
- they also increase the drag forces on the airplane that generates them, decreasing fuel efficiency.
The airflow around winglets is complex. Your wind tunnel should include smoke or fog in the airflow so that you can visualize streamlines along the length of the airfoil. Figure 2, illustrates some design considerations you may wish to consider for the winglets (Hepperle, 2006). A gradual curve transistioning from airfoil to winglet may help to reduce turbulent flow at the corner region. Translating the winglet toward the trailing edge of the airflow can also promote laminar flow at the trailing edge of the wingtip.
In this project, you will test airfoils built both with and without winglets in a wind tunnel. Do you see evidence for wing tip vortices when testing airfoils without winglets? Does the addition of winglets alleviate wing tip vortices? Do the winglets increase lift? For winglet-related project ideas that do not require a wind tunnel, see the Variations section.
Terms and Concepts
To do this project, you should do research that enables you to understand the following terms and concepts:
- airfoil,
- chord line,
- mean camber line,
- camber,
- aspect ratio,
- angle of attack,
- winglets,
- drag,
- lift,
- wing tip vortices.
Questions
- What are the forces acting on an airfoil in a wind tunnel?
- How will the addition of winglets affect these forces?
- How will the addition of winglets affect flight performance?
Bibliography
- You'll definitely want to check out NASA's Beginner's Guide to Aeronautics. This site is packed with useful information on the science of flight. The "Guided Tours" make it easy to navigate through groups of related pages:
NASA, 2005a. "Guided Tours of the Beginner's Guide to Aeronautics," NASA, Glenn Research Center [accessed June 8, 2006] http://www.grc.nasa.gov/WWW/K-12/airplane/guided.htm. - Here are some sources of information on winglets:
- ScienceIQ.com (n.d.). "Taming Twin Tornadoes," [accessed March 1, 2018] http://www.scienceiq.com/Facts/TwinTornadoes.cfm.
- Larson, G.C., 2001. "How Things Work: Winglets," originally published in Air & Space/Smithsonian, Aug/Sep 2001, available online: https://www.airspacemag.com/flight-today/how-things-work-winglets-2468375/.
- Hepperle, M., 2006. "A Close Look at Winglets," Martin Hepperle AeroTools [accessed June 9, 2006] http://www.mh-aerotools.de/airfoils/index.htm.
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Materials and Equipment
To do this experiment you will need the following materials and equipment:
- materials for building model airfoils, e.g.:
- balsa wood for framework,
- tissue paper covering,
- modeling knife,
- glue,
- airplane dope.
- (Alternatively, airfoil sections can be shaped from solid pieces of balsa or other wood.)
- wind tunnel for testing airfoils
Remember Your Display Board Supplies
 Poster Making Kit 
|
 ArtSkills Trifold with Header
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 Poster Lights
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Winglets in Wind Tunnels
www.sciencebuddies.org/science-fair-projects/project-ideas/Aero_p012/aerodynamics-hydrodynamics/winglets-in-wind-tunnels
Experimental Procedure
- Do your background research so that you are knowledgeable about the terms, concepts, and questions above.
- Construct two or more airfoils, identical in shape except for the presence/absence of winglets. See Figure 2 in the Introduction for ideas on different winglet designs you might wish to consider.
- Test your airfoils in a wind tunnel. The measurements that you are able to make will depend on the instrumentation available. Desirable measurements are:
- lift,
- drag,
- visualization of streamlines at the wing tip (using smoke or fog).
If you like this project, you might enjoy exploring these related careers:
Aerospace Engineer
Humans have always longed to fly and to make other things fly, both through the air and into outer space—aerospace engineers are the people that make those dreams come true. They design, build, and test vehicles like airplanes, helicopters, balloons, rockets, missiles, satellites, and spacecraft. Read more
Aerospace Engineering & Operations Technician
Aerospace engineering and operations technicians are essential to the development of new aircraft and space vehicles. They build, test, and maintain parts for air and spacecraft, and assemble, test, and maintain the vehicles as well. They are key members of a flight readiness team, preparing space vehicles for launch in clean rooms, and on the launch pad. They also help troubleshoot launch or flight failures by testing suspect parts. Read more
Pilot
Pilots fly airplanes, helicopters, and other aircraft to accomplish a variety of tasks. While the primary job of most pilots is to fly people and cargo from place to place, 20 percent of all pilots have more specialized jobs, like dropping fire retardant, seeds, or pesticides from the air, or helping law enforcement rescue and transport accident victims, and capture criminals. Pilots enjoy working and helping people in the "third dimension." Read more
Aviation Inspector
Aviation inspectors are critical to ensuring that aircraft are safe to fly. They conduct pre-flight inspections to make sure an aircraft is safe. They also inspect the work of aircraft mechanics, and keep detailed records of work done to maintain or repair an aircraft. As problems are identified, they may make changes to maintenance schedules, and may be called upon to investigate air accidents. Read moreVariations
- For a much more basic project on winglets using paper airplanes, see the Science Buddies project Why Winglets?.
- The simple folded airplanes used in the project just mentioned normally lack vertical stabilizers. Vertical stabilizers counteract imbalances in lift between the two wings, and thus resist forces that would tend to make the plane roll. In this simple type of paper airplane, winglets can function as vertical stabilizers. Another type of paper airplane (made with laminated construction methods) generally does include a vertical stabilizer as part of the design. For more details, see the Science Buddies project What Makes a Good Aerodynamic Design? Test Your Ideas with High-Performance Paper Gliders. Do winglets improve the flight characteristics of high-performance paper gliders?
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