In standard reference nomenclature it is generally listed as either Q or q.ĭynamic pressure = 1/2 x air density x velocity 2įree Stream Velocity: The velocity of air flow, undisturbed by the airfoil. Total wing drag = dynamic pressure x Wing Area x Drag Coefficientĭynamic Pressure: The amount of energy in the air flow. In standard reference nomenclature it is generally listed as Cd. The chord line is a straight line between the leading and trailing edge and is used as a standard reference in all airfoils.ĭrag Coefficient: A measure of an airfoil's resistance to air flow. A line mid-way between the upper and lower surfaces of an airfoil.Ĭhord: The distance from the leading edge to the trailing edge of the airfoil. The mid-point of an airfoil thickness profile. 1.0 represents the trailing edge.Ĭamber: Also known as the camber line or mean line. A value of 0.0 represents the leading edge. In AeroFoil, the transition points are given in dimensionless units of length, x / chord. Boundary layer thickness and drag increase very rapidly.īoundary Layer Transition: The point at which the boundary layer is said to transition from laminar to turbulent or separated and from turbulent to separated. Separation occurs when the boundary layer detaches from the airfoil surface and eddies are created.
The thickness and drag increases more rapidly. At some point, a laminar boundary layer will become turbulent. Laminar boundary layers are thin and create the lowest drag. There are three basic types of boundary layers laminar, turbulent, and separated. The thickness of the disturbed airflow is known as the boundary layer. At some small distance from the airfoil surface, the local air velocity is uniform. The molecules of air that are in direct contact with the airfoil surface are not moving. Aerodynamic Center: A point, near the quarter-chord location, about which the pitch coefficient is constant.Īngle of Attack: The angle of an airfoil, measured from the chord line, to the air flow.Īngle of Zero Lift: The angle of attack, measured from the airfoil's chord line, at which there is no lift.īoundary Layer: Air flowing along an airfoil does not have a uniform velocity.
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