Drag The Drag equation is: The coefficient of drag is the ratio of the drag pressure to the dynamic pressure. Drag like lift is proportional to the dynamic pressure of the air and the area on which it acts. The equation is much like the lift equation except that it measures the force in the stream-wise direction or parallel to the flow.
The Cd is obtained from wind tunnel testing Also note that the S is replaced with an A for area Also note that V occurs at the square, so double V and drag goes up 4 times as much. Induced Drag Induced drag is drag generated by the production of lift or more accurately by the production of wingtip vortices.
The DI formula is:. This downward component known as downwash, causes the airstream to depart at an angle downward from the incoming air.
The lift vector being perpendicular to the flow, is now tilted backward at half the downwash angle. Induced Drag This means some lift is being generated opposite to the flight path this rearward component is by definition drag. Induced drag is influenced by the CL and aspect ratio. It increases directly as the square of CL and inversely as the aspect ratio.
This inverse relationship is why long skinny wings generate higher CL. Induced Drag At low speed and low aspect ratio short wings induced drag is greatest. Induced drag varies inversely with the velocity squared. Parasite Drag Parasite drag is the drag caused by protuberances and increases directly with the velocity squared. The Dp formula is:. Parasite Drag Ski n Friction — Drag caused by rivets, dirty surfaces, effects boundary layer Form Drag — caused by the shape of the surface Interference — collision of boundary layers of different surfaces Leakage — pressure differences inside and outside the plane, like cracks in door seals Profile — drag with regards to moving helicopter rotors Drag Definitions pg 72 Total drag Total drag is the sum of induced drag and parasite drag.
Ground effect Ground effect usually happens when within one wingspan of the ground. The surface actually helps destroy the downwash generated by the wingtip vortices and thus forces the lift vector more to the vertical thereby reducing drag. Note; span is represented by b and height by h. Ground effect There is also a change in the effective angle of attack. Because of the altered downwash, an angle of attack increase is the result Pitching moments develop downward for an aircraft entering ground effect because of the wings downwash not being able to help the tail generate lift downward.
Please read this answer which tries to explain induced drag much more intuitively than what you probably have read until now. With more air flowing past the wing per unit of time at higher speed, less deflection is needed, so the backward tilt of the lift vector is smaller. Since the weight of the aircraft should not change with speed, the same aerodynamic force has a smaller backward component at higher speed or in denser air.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Does speed or angle of attack generally have the greatest impact on total induced drag? Ask Question. Asked 2 years, 11 months ago. Active 2 years, 7 months ago.
Viewed times. There are many factors which influence the amount of aerodynamic drag which a body generates. Drag depends on the shape, size, and inclination, of the object, and on flow conditions of the air passing the object.
For a three dimensional wing, there is an additional component of drag, called induced drag , which will be discussed on this page. For a lifting wing, the air pressure on the top of the wing is lower than the pressure below the wing. Near the tips of the wing, the air is free to move from the region of high pressure into the region of low pressure. The resulting flow is shown on the figure by the two circular blue-grey arrows with the arrowheads showing the flow direction.
As the aircraft moves to the lower left, a pair of counter-rotating vortices are formed at the wing tips. The line of the center of the vortices are shown as blue vortex lines leading from the wing tips. If the atmosphere has very high humidity, you can sometimes see the vortex lines on an airliner during landing as long thin "contrails" leaving the wing tips.
The wing tip vortices produce a swirling flow of air behind the wing which is very strong near the wing tips and decreases toward the wing root. The effective angle of attack of the wing is decreased by the induced flow of the vortices and varies from wing tip to wing root.
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