![]() The induced drag is an indication of the amount of energy lost to the tip vortices. Swirling vortices are formed at the wing tips, and there is an energy associated with these vortices. This drag occurs because the flow near the wing tips is distorted span wise as a result of the pressure difference from the top to the bottom of the wing. Aerodynamicists have named this component the induced drag. There is an additional drag component caused by the generation of lift. The component of the aerodynamic force that is opposed to the motion is the drag the component perpendicular to the motion is the lift. We can determine the magnitude of the force by integrating (or adding up) the local pressure times the surface area around the entire body. Since pressure is a measure of the momentum of the gas molecules and a change in momentum produces a force, a varying pressure distribution will produce a force on the body. As air flows around a body, the local velocity and pressure are changed. This source of drag depends on the shape of the aircraft and is called form drag. We can also think of drag as aerodynamic resistance to the motion of the object through the fluid. Along the solid surface, a boundary layer of low energy flow is generated and the magnitude of the skin friction depends on the state of this flow. For the gas, the magnitude depends on the viscosity of the air and the relative magnitude of the viscous forces to the motion of the flow, expressed as the Reynolds number. For the solid, a smooth, waxed surface produces less skin friction than a roughened surface. ![]() Because the skin friction is an interaction between a solid and a gas, the magnitude of the skin friction depends on properties of both solid and gas. ![]() We can think of drag as aerodynamic friction, and one of the sources of drag is the skin friction between the molecules of the air and the solid surface of the aircraft. While many of the factors that affect lift also affect drag, there are some additional sources of aircraft drag. Drag acts in a direction that opposes the motion. It makes no difference whether the object moves through a static fluid or whether the fluid moves past a static solid object. There must be motion between the object and the fluid. ![]() Drag is generated by the difference in velocity between the solid object and the fluid. For drag to be generated, the solid body must be in contact with the fluid. It is not generated by a force field, in the sense of a gravitational field or an electromagnetic field, where one object can affect another object without being in physical contact. It is generated by the interaction and contact of a solid body with a fluid (liquid or gas). How is drag generated?ĭrag is a mechanical force. Drag is generated by every part of the airplane, even the engines. Home > Beginners Guide to Aeronautics Drag Wright 1903 Flyerĭrag is the aerodynamic force that opposes an aircraft’s motion through the air.
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