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The drag curve or drag polar is the relationship between the drag on an aircraft ... If an aerodynamic surface is held at a fixed angle of attack in a wind tunnel, ...
It is measured empirically by testing in a wind tunnel or in free flight test. [1] [2] [3] The L/D ratio is affected by both the form drag of the body and by the induced drag associated with creating a lifting force. It depends principally on the lift and drag coefficients, angle of attack to the airflow and the wing aspect ratio.
A sample wind tunnel layout showing some typical features including a test section and control room, a machine for pumping air continuously through ducting, and a nozzle for setting the test airspeed. A wind tunnel is "an apparatus for producing a controlled stream of air for conducting aerodynamic experiments". [1]
The drag characteristics of a wing with infinite span can be simulated using an airfoil segment the width of a wind tunnel. [12] An increase in wingspan or a solution with a similar effect is one way to reduce induced drag. [6]: 4.10 The Wright brothers used curved trailing edges on their rectangular wings. [13]
The G7 drag curve model prediction method (recommended by some manufacturers for very-low-drag shaped rifle bullets) when using a G7 ballistic coefficient (BC) of 0.377 yields very similar results in the supersonic flight regime compared to the Doppler radar test derived drag coefficients (C d) prediction method. At 1,500 m (1,640 yd) range the ...
In wind tunnel tests, in which the angle of attack and airspeed remain constant, an increase in the lift coefficient ensues, [9] which accounts for the "floating" effect. Ground effect also alters thrust versus velocity, where reduced induced drag requires less thrust in order to maintain the same velocity.
Drag coefficients in fluids with Reynolds number approximately 10 4 [1] [2] Shapes are depicted with the same projected frontal area. In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.
A lift and drag curve obtained in wind tunnel testing is shown on the right. The curve represents an airfoil with a positive camber so some lift is produced at zero angle of attack. With increased angle of attack, lift increases in a roughly linear relation, called the slope of the lift curve.