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Camber: A measure of the curvature of the airfoil
The camber of the upper surface is more pronounced than the camber of the lower surface (usually somewhat flat).
Leading Edge: Forward-facing end that is rounded
Trailing-Edge: Rear-facing end that is narrow and tapered towards the rear
Chord Line: Reference line drawn from the centre of the leading edge straight through the wing till the trailing edge.
This reference line is used to find the magnitude of the upper or lower camber at any point along the wing (by measuring the distance between the chord line and the upper and lower surfaces of the wing).
Mean Camber Line: Another reference line drawn from the leading edge to the trailing edge.
However, unlike the chord line, this line is equidistant at all points along the wing from the upper and lower surfaces.
Airfoils are designed in such a way that the shape takes advantage of the air’s response to certain physical laws. Hence, two actions from the air are developed as the wing passes through. A positive or high pressure lifting action from the air mass below the wing, and a negative pressure lifting action from low pressure above the wing.
Teardrop wing profile results in the speed and pressure changes of the air passing over the top and under the bottom to be the same.
According to Bernoulli’s Principle, the faster a fluid moves, the lower its pressure. The slower a fluid moves, the higher its pressure. Airfoils are shaped to manipulate the flow of air to produce force. The design of the airfoil is dependent on aerodynamic characteristics and these characteristics depend on the speed, weight, and purpose of the car. There are essentially two types of airfoils - symmetrical and non-symmetrical. Symmetrical airfoil has identical upper and lower surfaces such that the chord line and mean camber line happen to be the same. Non-symmetrical airfoil, also known as a cambered airfoil, has different upper and lower surfaces such that the chord line happens to be placed above with large curvature. Furthermore, their chord line and chamber lines are different. The advantages of this type are a better lift to drag ratio and stall characteristics, thereby resulting in the production of a useful lift at zero angle of attack.
Camber in Design
The airfoil should be designed to maximize laminar flow to avoid pressure drag (as pressure drag is caused by a turbulent wake). For low traveling airfoils like a solar car, cambering the body is aerodynamically advantageous. NACA 66 airfoils are recommended for a basis for flat airfoils, but other optimized airfoils designs can be referenced for different car shapes. We may need to develop our own model to apply camber to a bullet design, as it’s shape varies about an axis.
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