Air transportation has become very useful and in flux due to the new technologies used. The theories, contributions and laws of aerodynamics are included and investigated in this paper work. The three laws of motion developed by Sir Isaac Newton have been very useful in explaining Why do airplanes/aircrafts fly?, and the law of Bernoulli for the theory of lift exerted by the wing of an airplane was also discussed here.
Aerodynamics of Airplane Wings
In the Grolier | Encyclopedia of knowledge they define aerodynamics as a branch of fluid mechanics dealing with the flow of air and other gases and of the forces acting on bodies moving through the gases, and the basic tools for aerodynamic research are the wind tunnels (vol. 1, p. 111). The laws of motion developed by Sir Isaac Newton underlies all other branches of theoretical mechanics, it explains the effects of forces acting on bodies either in motion or at rest, and the application of the law of motion was first applied by Daniel Bernoulli (vol. 1, p. 111).
They identify four main forces that act on an aircraft: thrust, gravity and the aerodynamic forces of drag and lift, thrust and drag work against each other, as do gravity and lift (vol. 1, p. 111). According to Anderson and Eberhardt in How Airplanes fly: A Physical Description of lift, Level 3 that one could understand easily aerodynamics by first focusing on the law of Newton rather than the law of Bernoulli, they identify 3 descriptions of lift, the first was Mathematical Aerodynamic Description that is used by aeronautical engineers, next is the popular explanation that is based on the Bernoullis principle, and lastly the physical description of lift which is based on the Newtons law (2007, ¶ 1-4).
In High School Subjects for Self Study Murray states the 3 laws of motion by Newton, first law is the law of inertia : Every body remains in its state of rest or of uniform motion in a strait line unless it is compelled to change that state by forces impressed on it., next is the law of acceleration : The force required to accelerate an object is proportional to the mass of the object and the acceleration given in it, lastly is the law of interaction : For every action, there is an equal and opposite reaction (vol. 2, pp. 550-558). In explaining the Bernoullis law, the Grolier | Encyclopedia of knowledge states that hes law, the pressure and velocity of moving liquids are in relation to each other (vol. 3, p.90). The testing of aerodynamic is performed expansively in combination with the theoretical research, the wind tunnels should have done most of the testing, some of the other wind tunnels are highly specialized that they can generate air flows in a short period or in an intermittent way in such with the large shock-tubes, computers also nowadays has been in a great help of testing wind tunnels (vol. 1, p. 112).
In an encyclopedia article, The Columbia Encyclopedia, states that aerodynamics is the study of gases in motion and its principal application is in the designing of an aircraft, aerodynamics is mostly concerned with flight but it can also be used in designing automobile and train bodies for minimum drag and in computing wind stresses on bridges, buildings, smokestacks, trees, and other structures, aerodynamic tool is consist of a wind tunnel that is basically a primary tool for aerodynamicists (vol. 1, p. 642). According to an encyclopedia article Visual fact finder that for a plane to fly, one should produce a lift or an upward force to overcome the weight in it and should also generate a forward thrust to overcome the rag or resistance of the air, and it is also stated that in a fixed-wing air craft the wings should be curved on the top and flat beneath, because the air that flows on the top is faster than that of the lower but the pressure beneath is greater than on the upper surface, thus producing lift (Williams et. Al, p.272).
Aerodynamics was already used in the 17th century, in The World Book Encyclopedia they listed the pioneers of aerodynamics, first is Leonardo da Vinci (see image 1) an Italian artist and scientist and the first man to study the flight of birds scientifically and the one who proposed flying machines, Sir Isaac Newton (see image 2) explained the behavior of force acting between an object and a fluid, for instance air, and not until the late 1800s did man first use aerodynamic principles to achieve flight in craft heavier than the air, Otto Lilienthal (see image 3) a German engineer who conducted experiments with wings for gliders and built a weighing system to measure the lift of experimental wings, another is Samuel P. Langley (see image 4) an American scientist who contributed one of the first scientific papers on aerodynamics, he published the Experiments in Aerodynamics in the year1891 and built a steam-driven model of an airplane, he flew the model but it was inadequate to carry a man, another pioneers are Orville and Wilbert Wright or the Wright brothers (see image 5) who spent three years of research to the development of the propeller-driven plane which they flew in 1903 and used such devices or wind tunnels and weighing systems to measure lift and drag (vol. 1, p. 79).
1899, in an internet article The History of the airplane, Part 3: The Wright Brothers first flight recorded that in the Wilbur brothers designed their first aircraft, a small, and biplane glider flown as a kite to test their solution for controlling the craft by wing warping. Wing warping is a method of arching the wingtips slightly to control the aircrafts rolling motion and balance and after the next three years, they started to design more gliders either it is flown unmanned or with pilots driving it, and they did not stop making new designs of gliders until 1911, they made their first airplane named Vin Fiz that was named after a grape soda company, the plane took 84 days of flight and stopping 70 times and it was the first plane to cross united states (¶ 1-3,14).
Many scientists, artist and engineers published their theories on aerodynamics; one of it is Leonardo da Vinci who drew a sketch on an aircraft model, on an article namely The Pioneers of Flight: Leonardo da Vinci by Dr. Hallion he states that Leonardo da Vinci can also be considered as a father of conceptual aerodynamics, the study of fluid flow because he found out that the behavior of the air is much more like the behavior of the water, generated theories on how a wing produces a lift force and proposed flying machines ( ¶ 3). Another published theory is the theory of Bernoulli and the law of force by Newton which has a greater relevance in aerodynamics of the twenty first century and on understanding the lift force exerted by the wings of an aircraft. In Explaining the lift, Bernoullis law, Coanda effect and the law of motion by Newton could be very useful, it was stated that Bernoullis principle states that the pressure of a moving gas decreases as its velocity increases.
When air flows over a wing having a curved upper surface and a flat lower surface, the flow is faster across the curved surface than across the plane one; thus a greater pressure is exerted in the upward direction but this theory does not explain fully the flight of an aircraft, scientist have been discussing that Coanda effect could explain the question Why do planes fly? it has been stated that Coanda effect, in which moving air is attracted to and flows along the surface of the wing, and the tilt of the wing, called the angle of attack, cause the air to flow downward as it leaves the wing. The greater the angle of attack, the greater the downward flow, In applying the third law of motion that needs an equal and opposite reaction, the airplane is deflected upward, it has been stated also that At the same time, a force that retards the forward motion of the aircraft is developed by diverting air in this way and is known as drag due to lift. Another kind of drag is caused by the slowing of air very near to the aircrafts surface; this can be reduced by making the surface area of the craft as small as possible. At low speeds the ratio between lift and drag decreases with gains in speed; accordingly, aerodynamic development for many years stressed increases in thrust over real reductions in drag (vol. 1, p. 642).
Lift, drag, gravity and thrust: four main sources that act on aircraft
According to the National Aeronautics and Space Administration, Four Sources of an Airplane written by Tom Benson, weight, lift, drag and thrust are the four major sources of that act on an aircraft (2007, ¶ 1-6). Weight as the force that is
Image source: NASA directed toward the center of the earth, He also says that The magnitude of the weight depends on the mass of all the airplane parts, plus the amount of fuel, plus any payload on board (people, baggage, freight, etc.). The weight is distributed throughout the airplane. But we can often think of it as collected and acting through a single point called the center of gravity. In flight, the airplane rotates about the center of gravity, next is the lift, as described earlier that the lift is the one who made an airplane to fly, Tom Benson also states that Lift is generated by the motion of the airplane through the air and is an aerodynamic force.
Aero stands for the air, and dynamic denotes motion. Lift is directed perpendicular to the flight direction. The magnitude of the lift depends on several factors including the shape, size, and velocity of the aircraft. As with weight, each part of the aircraft contributes to the aircraft lift force. Most of the lift is generated by the wings. Aircraft lift acts through a single point called the center of pressure. The center of pressure is defined just like the center of gravity, but using the pressure distribution around the body instead of the weight distribution, the third one is the drag, as an airplane moves in the air there is another aerodynamic force present, The air resists the motion of the aircraft and the resistance force is called drag.
Drag is directed along and opposed to the flight direction. Like lift, there are many factors that affect the magnitude of the drag force including the shape of the aircraft, the stickiness of the air, and the velocity of the aircraft states Benson., and finally, the thrust, in an airplane they use the propulsion system to overcome the drag and to generate a force called thrust, the magnitude of the thrust depends on many factors associated with the propulsion system including the type of engine, the number of engines, and the throttle setting (2007, ¶ 1-6).
In a software source Encyclopedia Britannica Deluxe Edition 2004 in the article Principles of aircraft flight and operation (From airplane),discussed that there are four sources acting on the flight of an aircraft, these forces are the lift which is the upward force exerted by the wing, next is the drag that act as the retarding force of the resistance to lift and to the friction of the aircraft moving through the air, third is the weight which is the downward effect that the gravity has on the aircraft and lastly, the thrust, the forward-acting force provided by the propulsion system, it has been stated that the drag and weight are elements inherent in any object including an aircraft and the lift and thrust are artificially created elements devised to enable an aircraft to fly (Aerodynamics).
Lift on an aircraft wing in application to Bernoullis law
In the College Physics, fourth edition, Sears et. Al. states that the orientation of the wing relative to the flow direction causes the flow lines to crowd together above the wing, corresponding to increased flow velocity in this region, much as in the throat of a Venturi, hence the region above the wing is one of the increased velocity and reduced pressure and in contrary below the wing the pressure remains nearly atmospheric, because the upward force on the under side of the wind is greater than the downward force on the top side, there is a net upward force or lift, this phenomenon can also be understood equally on the basis of Newtons law (Sears et. Al, p 220). in order for the fluid to exert an upward force on the wing, the wing must exert a downward reaction force on the fluid, deflecting the stream downward, the fluid suffers a net change in the vertical component of momentum as it passes the wing,.
Corresponding to the downward force of the wing exerts on it, the force of the wing is indeed upward (Sears et. Al, p 220). According mainly to the Grolier | Encyclopedia of knowledge, to overcome the earths gravity and rise into the air, an aircraft must be acted on by a lift force that is supplied mainly by the by the aircrafts wings, a wing or other surface designed to produce a desired effect when acted on by a flowing air is called an airfoil, the law of Bernoulli forms the basis for the theory of lift exerted on an airfoil in contrast with the wings, the cross section of the wing is designed so that when the wing meets the air it will cause the air to flow more rapidly past the upper surface of the wing than the lower surface, as a result, air pressure is above the wing than below it, resulting a lift (vol. 1, p 111).
In the book of Anderson the History of Aerodynamics, according to his illustration that on an airfoil the circulatory flow and the free stream are in the same direction that causes the increase of speed of the total flow, and on the bottom of the airfoil the direction of the circulatory flow and free stream are in opposite that causes the reduced speed of the total flow, as a result, the velocity on the top of the airfoil is higher than the velocity of the lower portion, in relation to the Bernoullis principle, the pressure on the top surface is lower than that of the lower surface of the airfoil that causes lift (Anderson, p. 245). As discussed by the Grolier | Encyclopedia of knowledge that the permission of an aircraft to fly is due to the lift or upward force, the upper surface of the airplanes wing is more curved than that of the lower thus air traveling across the wing is made to travel faster and the pressure on the upper surface is reduced and the greater pressure from the lower surface of the wing supplies lift (vol. 3, p. 90).
In a software Microsoft Encarta Reference Library 2004, airplanes fly because of the lift exerted by its wings that they pushes the air downward, the leading edge of an airplane wing is slightly higher than the trailing edge when the plane is maintaining altitude, as the wing moves through the air it pushes the air underneath the wing downward and the air in the upper surface of the wing follows the surface and deflected downward as the third law of motion states that in every action there is an equal and opposite reaction, as the air was pushed by the wing downward, the air pushes the wing up, Bernoullis principle was also used in explaining the lift of an aircraft, to have a decrease in pressure there should have an increase in the velocity of a flow of fluid and vice versa so the pressure on the upper side of an airplanes wing is lower than that of the lower surface of the wing (Aerodynamics).
There are four forces that act on aircraft, the lift, drag, thrust, and gravity. Each of them is essential in an aircraft. Aerodynamics is very useful in determining the aircrafts quality and safety because it is involve in making an aircraft. Today, aerodynamics is improving from time to time because of the higher technologies applied to it. Many artist, scientist and engineers formulated theories to prove the lift action of a plane, now their theories have been of a great help in fulfilling the dream of a man to fly like the birds do.
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