Dominique Hoskin Ellen Liverpool Matthew Vernacchia Sunny Wicks Chelsea He

1. Wind Tunnels …and other cool facts about airplanes Dominique Hoskin Ellen Liverpool Matthew Vernacchia Sunny Wicks Chelsea He

2. Efficiency Which shape makes the best wing? A) C) B) D)

3. Diagram Lift Thrust Drag Weight Intro to Aerodynamics Ppt by Professor Darmofal

4. Lift Bernoulli Lift Forces – Due to pressure difference Newtonian Lift Forces – Due to airstream redirection How do planes remain in flight? Source: http://www.pbs.org/wgbh/nova/space/lift-drag.html

5. Factors affecting Lift Airfoil Shape Angle of Attack Source http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html

6. Lift Forces The Bernoulli View By Bernoulli's Principle, the faster flowing airstream exerts less pressure on the wing There is an upward force on the wing DEMO in wind tunnel -look for splitting airstreams • Airfoil shape & orientation force air to flow faster over top side of the wing than over the bottom side of the wing Source: http://www.pbs.org/wgbh/nova/space/lift-drag.html

7. Lift Forces The airfoil redirects the air stream. It approaches the airfoil flowing horizontally, and leaves it flowing slightly down Since the direction of flow changed, the air's momentum changed → There must be a force from the wing pressing down on the air → There must be a force from the air pressing up on the wing More angle of attack → more downward redirection → more lift (generally) DEMO in wind tunnel – observe downward redirection of air stream The Newtonian View

9. Stall If a greater angle of attack leads to more lift, why not increase it indefinitely? Eventually, the angle of attack becomes so large that stable airflow is impossible, and the airstream breaks up into vortexes This causes a loss of lift know as stall. Stalling leads to loss of control of the plane. DEMO in wind tunnel – look for stall vortexes Source: http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html

10. How Can Planes Fly Upside-Down? By changing the angle of attack, lift can be generated in either wing orientation: Challenge Source http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html

11. Drag “Friction” between air and wing → rough surfaces have more drag Force to redirect airflow → boxy surfaces with large area have higher drag. Sleek, narrow surfaces have less drag

12. Thrust The Fundamentals • Thrust is the force that generated by the propulsion system of an aircraft. • Thrust is needed to overcome the drag force and push an aircraft forward. • In order to keep aircraft in flight, a certain velocity must be maintained so that there is enough lift to overcome the weight of the aircraft. Source: http://www.nasa.gov/images/content/459719main_x51-b-800.jpg

13. Propulsion Systems How they work • Propulsion systems use concepts of Newtonian mechanics. • Newton’s third law states that for every action there is an equal and opposite reaction. • Propulsion systems accelerate some type of fluid towards the rear of the aircraft, thus generating a Thrust force in the opposite direction. • Newton’s second law states that force is equal to mass times acceleration. • The thrust of a propulsion system, or the force produced by an aircraft engine, is equal to the change in momentum of the fluid being accelerated. • Momentum is the product of the mass and velocity. Source: http://upload.wikimedia.org/wikipedia/commons/thumb/3/39/GodfreyKneller-IsaacNewton-1689.jpg/225px-GodfreyKneller-IsaacNewton-1689.jpg

14. Propellers • A propeller is like a rotating wing. • It also has an airfoil shape and produces thrust the same way a wing produces lift. • For propellers, air is the fluid that is being accelerated. • Propellers can be made to rotate by a variety or power sources. Sources: http://static6.depositphotos.com/1061433/540/i/450/dep_5402863-Civil-propeller-plane.jpg http://canitbesaturdaynow.com/images/fpics/1750/1e51032f6182f1dee9230ea875109779.jpg

15. Propellers • The power source must turn a shaft very quickly to generate a significant amount of thrust. • The first propellers were powered by internal combustion engine. • Since that time propellers have also been powered by gas turbine engines on even human powered bicycle-like machines.

16. Gas turbine engines are the most common type of jet engines. • In gas turbine engines the fluid being accelerated is a combination of air and fuel. Gas Turbine Engines • Air is taken into the gas turbine engine through an inlet, pressurized in a compressor, mixed with fuel and combusted in a burner, passed through a turbine that turns a central shaft, and is funneled and released through a nozzle that produces thrust. Source: http://www.grc.nasa.gov/WWW/k-12/airplane/turbparts.html

17. Compressors • The job of a compressor is to increase the pressure of the air as it moves from one end to the other. • The two main types are axial and centrifugal but axial is much more common in modern aircraft. • Axial compressors contain rotating airfoil shaped blades connected to the central shaft called rotors, and non-rotating airfoil shaped blades called stators. • The blades of the rotors and stators are very close together and an axial compressor will have several rows of each. • As the rotating blades force air through the compressor, the stators keeps the airflow straight and gradually increase the pressure of the air. Sources: http://www.free-online-private-pilot-ground-school.com/images/dual-spool-compressor.gif

18. Burner • Burners contain combustion chambers made of an inner liner and an outer casing. • They can either have just one combustion chamber or several around the center shaft. • In the burner the compressed air is mixed with fuel and is burned in processes known as combustion. • Combustion is a process that requires fuel, oxygen, and heat and produces exhaust gasses and heat. • This hot exhaust gas is responsible for the thrust produced. Sources: http://www.firstscience.com/home/images/stories/articles/jet1.jpg http://www.century-of-flight.net/new%20site/images27/Multcomb.gif

19. Power Turbine • The hot exhaust gas from the burner turns the power turbine. • A turbine is very similar to a compressor. • It too has rotors and stators that are airfoil shaped. • The rotors of a turbine are attached to the central shaft as in a compressor. • The hot exhaust gas turning the turbine and central shaft is what drives the compressor. • Aircrafts can have multiple turbines but have much fewer turbines than compressor stages. Source: http://turbine-turbines.com/wp-content/uploads/2011/12/turbines-blade1.jpg

20. Nozzle • The nozzle is where the thrust is produced and where the hot exhaust gas is released. • A nozzle is simply a tube that directs and controls the flow of the hot exhaust gas. • In the nozzle the exhaust gas is accelerated so it leaves the engine at high velocity. • Since the momentum of the air and fuel has been drastically increased, a large thrust force is produced in the opposite direction of the airflow. • Nozzles come in many different shapes and sizes and are determined by the needs of a particular aircraft. Source: http://www.grc.nasa.gov/WWW/k-12/airplane/nozzle.html

21. Thanks • Gelb Shop • Todd and Company • Professor Darmofal • Sunny Wicks • Chelsea He • Dave Robertson