Basic Aerodynamic Theory
An Aerofoil is the shape of a wing or blade (rotor, propeller or turbine).
There are 6 main wing designs
Leading Edge – A part of the aerofoil that makes contact with the air first
Trailing Edge – A part of an aerodynamic surface that is at the rear edge. This is where the airflow separated by the leading edge rejoins. Control surfaces can be placed here to redirect airflow and control the aircraft (ailerons, rudder, flaps.etc.)
Chord – If you image a straight line going from the leading edge to the trailing edge, in the direction of the airflow, this is a chord or chord length. It is used to measure the width on a aerofoil.
Chord Line – The chord line is the straight line going from the leading edge to the trailing edge of the aerofoil.
Camber – Camber refers to asymmetry between the top and lower surfaces of an aerofoil. An aerofoil that is not cambered is called a symmetrical aerofoil (See graph in 12.6.2).
Thickness – The thickness is measured from the chord line and varies along the length of the chord, there are two ways to measure the thickness, one measuring perpendicular to the camber line and the other, perpendicular to the chord line.
Relative airflow is the direction of the atmosphere relative to an aerofoil. It is the opposite direction the the travel of the aerofoil. It is the angle of the chord line that defines the angle of attack (AOA). The AOA is of high importance because exceeding the critical angle of attack the plane will be in a stall, regardless of airspeed (see 12.6.30)
Bernoulli’s Theorem explains how lift is produced on an aerofoil.
This principle was first used to explain changes in the pressure of fluid flowing within a pipe whose cross-sectional area varied. In the wide section of the gradually narrowing pipe, the fluid moves at low speed, producing high pressure. As the pipe narrows it must contain the same amount of fluid. In this narrow section, the fluid moves at high speed, producing low pressure.
High speed airflow is associated with low pressure and low speed airflow is associated with high pressure. The aerofoil is designed to increase the velocity of airflow above its surface which in turn decreases pressure above the aerofoil. The impact of air on the lower surface of the aerofoil increases pressure below at the same time. It is this combination of pressure decrease above and pressure increase below the produces lift.
Laminar Flow (also called Streamline Flow) is the smooth and uninterrupted flow of air over aerofoils (or other parts of an aircraft) in flight. If the smooth flow of air over an aerofoil is interrupted, it results in turbulence – causing a loss of lift and an increase in drag.
Static Pressure is not affected by airspeed. The static port is normally installed at a 90 degree angle to airflow. Static pressure increases with Altitude (This is how your altimeter works)
Dynamic Pressure is measured in a pitot tube and is affected by both the air density and aircraft speed. It is mathematically expressed as 1/2 p v2. This shows that dynamic