1.1 Background Research
Aviation has come a long way since it started, with a history spanning over two thousand years, with kites and gliders as pioneers of aircrafts. People mostly rely on airplanes to get them across countries in the modern day. In the ancient times, people went overseas by boats or ships, before the discovery of hydrogen.
Sir George Cayley, regarded as one of the most important people in the history of aeronautics, built his first aerial device in 1796, a human glider (Crouch,2004). He was also the first to identify the four aerodynamic forces of flight, weight, lift, drag, thrust and their relationship (CTIE,2002). He observed that birds could soar for long distances by twisting their arched wing surfaces, therefore deducing that fixed-wing machines would fly if the wings were cambered (CTIE,2002). This was the first scientific testing of airfoils, the part of the aircraft that is designed to produce lift (CTIE,2002).
Lift is the force that directly opposes the weight of an airplane and holds the airplane in the air (Anderson et al, 2001). The Bernoulli effect, which relates the speed of the air to the static pressure, produces a reduced static pressure above the wing, creating lift(Anderson et al, 2001). Lift is generated by every part of the airplane, but mostly generated by the wings on a normal airliner. It is a mechanical aerodynamic that is generated by the motion of the airplane through the air. As lift is a force, it is a vector quantity, having a magnitude and a direction associated with it (Anderson et al, 2001). Lift acts through the center of pressure of the object and is directed perpendicular to the flow direction (Anderson et al, 2001). There are several factors which affect the magnitude of lift. Lift is created by turning a flow of air. An airfoil, curved, will turn a flow. These factors can be grouped into those associated with the object, those associated with the motion of the object through the air, and those associated with the air itself (NASA, 2015):
Object: At the top of the figure, the wing has a large effect on the amount of lift generated (NASA, 2015). The airfoil shape and wing size both affect the amount of lift, so does the ratio of the wing span to the wing area (NASA, 2015).
Motion: To generate lift, the object needs to move through the air (NASA, 2015). The lift depends on the velocity of the air and how the object is inclined to the flow (NASA, 2015).
Air: Lift depends on the mass of the flow. The lift also depends in a complex way on two other properties of the air: its viscosity and its compressibility (NASA, 2015).
The factors that affect lift are gathered to form a single mathematical equation called the Lift Equation. We can predict how much lift force will be generated by a given body moving at a given speed using the lift equation (NASA, 2015).
According to Anderson et al (2001), there is both the mathematical and physical description of life. Aeronautical engineers use the mathematical description of lift, which uses complex mathematics, computer simulations and is a powerful design tool (Anderson et al, 2001). The velocities of air around the wing are usually generated using a program. Then the pressures and lift forces are calculated accurately using Bernoulli’s equation (Anderson et al, 2001). As this is often used to calculate the lift of a wing, it is quite common with the popular description of lift (Anderson et al, 2001).
The theories in the mathematical description of lift do not illustrate the fact that lift requires the action of a great deal of air like the popular description of lift (Anderson et al, 2001). To accurately compute the aerodynamics of a wing, these are the tools to use, although the description will be mathematical and not physical (Anderson et al, 2001).
The wing is mainly used to generate lift. The wing also has two other productions, drag force (D) and nose-down pitching moment (M) (Sadraey, 2012). While it is important to maximise the lift, a wing designer is looking to maximize the lift, the other two (drag and pitching moment) must be minimized (Sadraey, 2012). In fact, a wing is considered as a lifting surface that lift is produced due to the pressure difference between lower and upper surfaces (Sadraey, 2012).
An airfoil is a shape that is designed to produce lift. It is the shape seen in the slice of the wing. The design of the airfoil largely affects the amount of lift produced from the wings. Characteristics that must be considered in selecting a wing include lift at cruise angle of attack, drag, stall characteristics, laminar flow, and room for internal structures (Sadraey, 2012). An airfoil has a leading edge and a trailing edge (Anderson et al, 2001). A chord and a camber also characterize an airfoil (Anderson et al, 2001). A chord is an imaginary straight line connecting the leading edge with the trailing edge (Anderson et al, 2001). It is used to determine the geometric angle of attack the area of a wing(Anderson et al, 2001). Camber is the asymmetry between the top and bottom surfaces of an airfoil (Anderson et al, 2001). The design of an airfoil can be determined by the chord and camber. Different designs of airfoils results in different amounts of lift and speed. With advances in technology, designing airfoils are considerably easier compared to the past. If the mean camber line is in a straight line, the airfoil is a symmetric airfoil, otherwise it is a cambered airfoil (Sadraey, 2012). The camber of an airfoil is usually positive. In a positive cambered airfoil, the upper surface static pressure is less than the ambient pressure, while the lower surface static pressure is higher than the ambient pressure (Sadraey, 2012). This is due to a higher airspeed at upper surface, while a lower speed at lower surface of the airfoil (Sadraey, 2012). When the airfoil angle of attack increases, the pressure difference between upper and lower surfaces increases (Sadraey, 2012). Airfoil designs consists of Low Camber, Deep Camber, Symmetrical and Low Lift.
Through advancement in technology, more airfoils designs are created to improve planes and generating more lift, drag, etc. Lift is a force that is generated by the wings to keep the plane in the air.
1.2 Research Questions
Does the shape of an airfoil affects its lift?
How does the shape of an airfoil affect its lift?
If the shape of an airfoil affects its lift, what is the difference in lift for different shapes of airfoils?
The deep camber airfoil design would have a higher lift than the low camber and symmetrical airfoils.
The independent variable is the shape of the airfoil while the dependent variable is the lift of the airfoils.