Aerodynamics Lecture 1 Chapter 1 What is Aerodynamics

Aerodynamics Lecture 1 Chapter 1

What is Aerodynamics? How does the text define Aerodynamics?

Aerodynamics defined • Is the science that deals with the motion of air and the forces on bodies moving through the air. • The term aerodynamics implies the explanation of why and how airplanes fly.

Why do we need Aerodynamics? • Pilots, Technicians, and others with an interest in aviation have a need to understand the behavior of the air and its effect on the airplane.

Chapter 1 History of Flight

Greek Mythology • The story of Daedalus and his son Icarus. – They utilized flight as a means of escape from the island of Crete where they were imprisoned. – Icarus flew too close to the sun and the heat melted the wax in his wings. – He fell to the sea and suffered one of the first fatal crashes in history.

What famous artist dreamed of flight? He cut off his ear.

Leonardo da Vinci • He was obsessed with the idea of transforming the muscle-power of man into lift and thrust through a flapping device called the ornithopter. (figure 1 -3 p. 3)

Aerostatics • How does a balloon fly? – The buoyancy principle discovered by Archimedes. – The pressure in any fluid, liquid, or gas, increases in depth. – Explain the phrase, ” high to low look out below? ”

Example • A small chunk of fluid within a larger container of fluid. – The pressure on the bottom of the surface is greater than the pressure on the top of the surface. – If the chunk of fluid had no weight , it would be pushed upward by the increased pressure of the bottom; however, the weight of this chunk of fluid added to the pressure force on the top surface balances out the increased pressure. (Static or still)

Example • Now suppose that this chunk of fluid is replaced by a container filled with a fluid lighter than the surrounding fluid. • The total weight of the container and the fluid inside it must be considered. – This total weight must be less than the weight of the amount of fluid displaces in order for it to rise.

Balloons • The previous example is the principle that causes a balloon to ascend. – Heated or lighter-than-air gas is placed inside the balloon. – When the resulting weight of the balloon and the gas inside it is less than the surrounding air, the balloon ascends.

Why does the balloon not rise to the top of the atmosphere? • The balloon, which has a gas of a certain density inside, rising in the atmosphere. • Eventually it will reach an altitude where the density of the outside of the balloon and the density inside the balloon are the same. – At this point the forces are again in balance and the pressure is not great enough to push the balloon upward. (figure 1 -7, p. 7)

Balloons • Balloons are referred to as aerostatic vehicles, which means that they will lift in a static air mass. • The balloon has no mechanism to move horizontally in this air mass. (only velocity and wind direction)

Joseph & Etienne Montgolfier • The brothers designed and built the first hot air balloon in France in June of 1783. (figure 1 -4, p. 4) • They did not know what caused their balloon to ascend. (they thought burning wood released some unknown gas that mysteriously caused objects to rise. ) • The principles of lighter than air soon became known and both hot-air and hydrogen-filled balloon flights were launched before the end of that year.

Hot Air Vs. Lighter than Air Gas • Hot air may be used at lower altitudes, however, at higher altitudes the temperature decreases causing the hot air to cool. • Lighter than Air Gas is used in high altitude flight.

Compressibility • Remember that air is compressible unlike water. • Air is compressed by its own weight. • Because all of the air is above the surface, the highest compression and highest density altitude occurs at the surface. • As you go up in altitude, there is less air above causing the compression at that altitude; therefore the air is less dense.

Airship • A lighter-than air craft with propulsive capability. • Fuel is required only to provide propulsion and not lift, as it is with other types of aircraft.

Heavier-Than Air Flight • Men attempted to emulate the birds, wing flapping and gliding. – One of the first persons to recognize the fixedwing mode of flight was an English nobleman, Sir George Cayley. – He was the first to recognize the importance of stability and control in an aircraft and designed his tail sections accordingly.

Sir George Cayley • In 1853 Cayley designed and built a humancarrying glider. – His coachman was pressed into service as the pilot and made the 1 st manned flight of a heavier-than air craft in history. – The coachman promptly resigned after the experiment. – Cayley’s work was published however it was not recognized until recently.

Otto Lilienthal • A German engineer that approached the idea of flight with scientific reasoning and analysis. • Lilienthal made many successful glider flights but crashed before he was able to achieve his ultimate goal of powered flight. – Figure 1 -8 on p. 9 shows Lilienthal’s design.

Octave Chanute • A Chicago engineer, was experimenting with gliders around the same time as Lilenthal. • Chanute was also scientific in his approach and contributed significantly to the structural soundness of aircraft design. – Figure 1 -9, p. 9 shows Chanute experimenting with gliders.

The men who recognized all of the problems involved with flight? They worked in a bicycle shop!

Wilbur & Orville Wright • Their procedure was methodical and scientific in the approach. • They studied the successes and failures of others especially Lilenthal and Chanute. • They tackled one problem at a time: construction techniques, devising controls, teaching themselves to fly, & increasing the efficiency of design.

December 17, 1903 • World’s First Sustained, Controlled, and Powered Flight! – Where? – Who was the pilot? • How did they decide who would pilot?

The Science of Aerodynamics • Gliders are _______ machines. • The study of moving air and the forces that it produces is referred to as ______, meaning literally, “air in motion” • Aerostatic means ______.

Classical Theory of Flight • Scientists began around 1910 to look into the physical principles of winged flight including behavior of wings & airfoils. • Frederick Lancaster in England • Ludwig Prandtl in Germany • Joukowsky in Russia – These men were scientists with the intent to explain physical behavior; not interested in developing aircraft.

Quiz on Lecture 1 Please take out a sheet of paper. Include today’s date and your name.

Quiz on Lecture 1 • Please explain how a balloon ascends to 10, 000 feet and remains at this altitude? • How did Cayley’s approach to achieving manned flight differ from Da Vinci’s? • What was the key to the Wright brother’s success? • What did scientists like Lancaster, Prandtl, & Jaoukowsky contribute to the development of the first airplane? • Why do we need to study aerodynamics?