What are the features of supercritical airfoil?
Supercritical airfoils are characterized by their flattened upper surface, highly cambered (“downward-curved”) aft section, and larger leading-edge radius compared with NACA 6-series laminar airfoil shapes. Standard wing shapes are designed to create lower pressure over the top of the wing.
How does supercritical airfoil work?
A supercritical airfoil is a special airfoil designed to reduce the drag when operating near supersonic speeds. When a plane flies near supersonic speeds, the air moving over the wing goes faster than the speed of sound before the plane does.
What is the principle behind the design of a supercritical airfoil?
Supercritical wings have a flat-on-top “upside down” look. As air moves across the top of a SCW it does not speed up nearly as much as over a curved upper surface. This delays the onset of the shock wave and also reduces aerodynamic drag associated with boundary layer separation.
What is a reflex airfoil?
An airfoil where the camber line curves back up near the trailing edge is called a reflexed camber airfoil. Such an airfoil is useful in certain situations, such as with tailless aircraft, because the moment about the aerodynamic center of the airfoil can be 0.
What causes drag divergence?
A: Drag divergence occurs when the drag on an airfoil starts to increase faster as the Mach number increases. Drag is the force of flight that acts against motion. Mach number measures speed in terms of the speed of sound.
What is an Undercambered airfoil?
The undercambered foil is what is often called a “one speed airfoil’, and a flat-bottom or semi-symmetrical foil is more adept at cutting through the air with less drag. Look at the polars for each airfoil type and you will see the relationship between camber and thickness, as Ollie outlined.
What is the mean camber line of an airfoil?
Mean camber line is a line joining the leading and trailing edges of an aerofoil, equidistant from the upper and lower surfaces; Maximum camber is the maximum distance of the mean camber line from the chord line; Maximum thickness is the maximum distance of the lower surface from the upper surface.
What is pressure drag?
Pressure drag is generated by the resolved components of the forces due to pressure acting normal to the surface at all points. It is computed as the integral of the flight-path direction component of the pressure forces acting on all points on the body. Form drag (sometimes known as boundary-layer pressure drag).
Why do shock waves cause drag?
The higher pressure behind the shock wave and lower pressure behind the expansion wave result in a single force that pushes the wing up and back. The upward part of this force is lift; the backward part of this force is drag.
What is Mach trimmer?
A Mach trimmer is a device which varies the pitch trim automatically as a function of Mach number to oppose Mach tuck and maintain level flight.