Aircraft and Automotive Systems - Assignment Example

Name Professor Course Date ME110 Aircraft and Automotive Systems Assignment Aerofoil is the shape of a wing of an aircraft as seen in its cross section. The air shaped body will move through a fluid as it produces aerodynamic forces. Moreover, air flowing past the wings will exert a force on them. In this regard, lift, which is a component of aerodynamic force, will act perpendicularly to the direction of oncoming airflow. On airplane, lift is the force that is generated by wings and propellers to keep the craft in the air. It contrasts with drag force since the latter is the component of surface force, which is parallel to the airflow direction. Misconception about Lifts Many texts have referred to the Bernoulli’s equation noting that it is the larger velocity of the craft that causes lower pressures upward. In this case, there will be a net pressure being generated upward. Using a sheet of paper held with both hands, while one blows air along its surface, it would tend to rise. This is because the average velocity on the upper surface has become greater and therefore lower pressure than that of the lower surface due to the blowing of air. According to the Bernoulli’s principle, when the upper part of the paper experiences lower pressure than the down side, the paper will be caused to rise. As one of the common misconceptions, it is the distance between the stagnation point and leading edge that cause lifting. However, according to Babinsky(497), this is not the condition for the craft to fly; what matters is the angle of attack but not necessarily the distance around the lower and the upper surface. There is also a misconception that wings causes lifting since the lower and the upper air particles meets at the trailing point at the same time. This has been disapproved using the smoke experiment. When smoke is set at leading edge, the wing divides its particles, to move both on upper and lower surfaces but there is no proof that particles beginning at the same time at leading edge will again meat at the trailing point. Specifically, when the lift is being generated, the air particles on the upper surface will reach the trailing edge before those that travel on the lower surface. By the demonstration, using the piece of the paper, Babinsky note that it is not really the demonstration of the Bernoulli’s principle. Although demonstrations have shown that when air is blown above the curved piece of paper it will rise, it is only possible because it is moving at different speeds on both sides. According to him, the pressure on both sides, lower and upper sides of the paper, are the same despite the likely differences in velocity. Therefore, it will be false to make such a connection using the Bernoulli’s principle/equation (Babinsky 497- 500). How Aerofoil Really Generates Lift The traditional explanation of what generates lift in the aircraft has been that since the top surface of its wings are curved, it will cover greater distance as compared to the bottom edge, which is flat. Therefore, the air will move faster on the upper part than that on the lower one causing greater pressure on top. However, Holger Babinsky has refuted the claim noting that although the lift will be caused by pressure, it ill result from change in the air flow as it meets the rounded leading edge of the wing but not the speed. On this shape of the aerofoil, depending on the angle of attack, wings will be forced upward since due to the attacking angle, they will be tilted to deflect air. The air behind the wing will be flowing downwards while that far ahead of it will not. Therefore the wing’s trailing edge should be sharp aiming diagonally downwards if it has to create greater lift. Both the upper and the lower part of the wing act to deflect air. This is because in a Coanda effect, the upper surface will be deflecting the air downwards so that the air flows while attached to the surface of the tilted wing. To explain this air inertia, when the wing has passed by, air will remain flowing downwards. Airplanes, therefore more specifically, fly due to the Newton’s 3rd law, Conservation of Momentum Law and the Coanda effect. For Newton’s law, since aerofoil will deflect air as it moves over it, exerting force on air to change its direction, the air must exert the same equal force but in the opposite direction. In the case of an aircraft, the wings exert down ward force on air, while the air will exert upward force, hence bringing the lifting effect (Beauty pars. 2-4). Why Is An Aerofoil Shaped As It Is? Aero planes have aerofoil that are rounded and not pointed at the front, thicker in the middle, tapered at the rear, flatter underneath, with a camber making it curve on top. This is because; the camber (humplike structure made on top) makes the air to flow on top of the wing faster than that flowing below it. On the lower side, it is made flat to maintain the air passing below it so that it can flow slowly, exerting higher upward pressure and therefore to keep it lifted. The aerofoil is capable of creating the lift depending on air while the airflow remains smooth. This is because it is rounded at the front tip. It is considered that up to a certain angle of attack, the flow will still be smooth. The wing’s trailing edge should be sharp aiming diagonally downwards if it has to create a greater lift What other shapes will generate lift?  (will a house brick generate lift? a saucer? a football? Draw some shapes) Shapes of Fans, sails, keel centerboards, compressors, baseball, propellers, and turbines among others. A baseball A sail Causes of Drags A drag is a force that acts opposite to the relative motion of an object moving in fluid. The force solely depends on velocity. The drag force will therefore decrease the velocity of the fluid relative to the object in fluid path. In aerodynamics, drags normally occur due to the creation of lift on lifting body of three-dimensional objects like wings or fuselages of aircrafts, when they redirect air to cause lift. There two types of aerodynamic drags: induced drag and parasite drag. For induced drag, it is a byproduct of lift. According to Isaac Newton, when a lift is produced, there must be an equal and opposite action reaction force and it is greatest when the angle of attack is greatest. Moreover, it will increase as the speed of the craft reduces. Parasitic drag is normally caused when a solid object moves through a fluid due to viscous pressure, or surface roughness, and the presence of multiple objects in relative proximities. Boundary Layer Generally, a boundary layer refers to the layer of fluid surrounding a body surface where the effects of viscosity can be felt. In aerodynamics, Ludwig Prandtl simplified the equation by categorizing the flow field into two areas. This is because the boundary layer when affected by the object will display airflow component that is different between the leading edge and the trailing edge. The first area was the one that is inside the boundary equation where there is a lot of viscosity and thereby creating a lot of drag that will be experienced by the boundary body. The other area would be negligible since it cannot cause any significant effect on the object. Boundary layer is considered thinner at the leading edge and thicker at the trailing edge of an aircraft.The fluid in the boundary layer is normally subjected to shearing forces. So long as the fluid is in contact with the surface of the body, a range of velocities will exist in the layer, from zero to maximum. What Are Wingtip Vortices and What Causes Them These are circular air rotating patterns that are left behind as the plane’s wings as they generate lifts. The vortex of one wing will trail from its tip. In this regard, they have been named as lift-induced or trailing vortices because they occur at the wings’ tips. It eventually develops into large vortices at the wing tip, especially at the areas where there are abrupt changes in platform of the wing. This is so especially around flap devices. Causes of Vortices These phenomena of the wingtip vortices are caused by the difference in pressure between the lower and the upper surfaces of the wings. As the air of the lower surface of the wing flows from centre of the wing or fuselage, to the tips, it will tend to curl itself as it flows towards the upper surface of the wing. It should be noted that since the plane is moving forward, there will be ‘tornado’ like horizontal structure emanating from the two wing tip and it has been regarded as one of the elements of Aerodynamics. As it can be seen from the plane, the left hand wing will have its wingtip vortex trailing clockwise while the right wing will be circulating in anti-clockwise direction. Since the two vortices are circulating in opposite directions, they will not merge. They will continue dissipating slowly and lingering in the atmosphere, a long time after the aircraft has passed. What are the common formulas for L & D?   What do they depend on?   (i.e CL, CD)   Give an example use of the equations. Ratio = Lift/Drag = L/D = cl/cd= 1/tan (a) = d/h= distance/ height It is important to note that the forces acting on the wing of an aircraft is weight, lift, drag and thrust. Secondly, the drag and lift are aerodynamic forces depending on the size and shape of the aircraft, velocity of the flight and air condition. Lift is drawn directly perpendicular to the path of the flight while the drag is shown along the path of the flight. Since the two forces belong to aerodynamics, the ratio that puts lift to drag indicates the efficiency of airplane aerodynamic. Large L/D ration will produce a large lift or a very small drag. The lift L equation is equal to one-half of the square of velocity V X air density r times X lift coefficients Cl X wing area A. L= 0.5 x Cl x r x V2 x A The drag D equation is presented as D= 0.5 x Cd x r x V2 x A Cd=drag coefficient Therefore, aerodynamic equation will be given by L/D = Cl/Cd (National Aeronautics and Space Administration n.p.) Conclusion As it has been noted, contrary to traditional belief about what determines efficient lift and speed of the aircraft, the design of the aerofoil, especially its angle of attack matters a lot when these objectives are to be met. Although the mechanism of lift has been termed to rely greatly on the Newton's second and third laws, Coanda effects and the Bernoulli’s principle, to achieve the optimal results, the aerofoil should be made rounded and not pointed at the front, thicker in the middle, tapered at the rear, flatter underneath, with a camber making it curve on top. This will also require that the designers take into account reducing the effects of viscosity in the boundary layer and those of drag forces. This happens to achieve the greatest aerodynamic efficiency so that the plane can lift and move easily. Works Cited Babinsky, Hogan.IOP Science. How Do Wings Work. Physics Education, 38(6), 2003. Beauty, Wliiam J.Why Does Smoke 'Ring'. amasci, 2003.2013, Online National Aeronautics and Space Administration. Lift to Drag Ration, 2013. 2013, Online Read More