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Lift and drag are the two components of the total aerodynamic force acting on an aerofoil or aircraft.. In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air.
The power is equal to the drag force times velocity. For aircraft in cruise flight the lift is equal to the weight (L=mg) and the engine thrust is equal to the drag (T=D). Hence, ϵ = P / ( m g v ) = D / L = 1 / f {\displaystyle \epsilon =P/(mgv)=D/L=1/f} , with f=L/D the lift-to-drag ratio , so the specific resistance of airplanes is roughly ...
The drag curve or drag polar is the relationship between the drag on an aircraft and other variables, such as lift, the coefficient of lift, angle-of-attack or speed. It may be described by an equation or displayed as a graph (sometimes called a "polar plot"). [1] Drag may be expressed as actual drag or the coefficient of drag.
The Lanchester-Prandtl lifting-line theory [1] is a mathematical model in aerodynamics that predicts lift distribution over a three-dimensional wing from the wing's geometry. [2] The theory was expressed independently [3] by Frederick W. Lanchester in 1907, [4] and by Ludwig Prandtl in 1918–1919 [5] after working with Albert Betz and Max Munk ...
The ratio between these two coefficients is the thickness ratio: ,, The lift coefficient can be approximated using the lifting-line theory, [4] numerically calculated or measured in a wind tunnel test of a complete aircraft configuration.
Lift coefficient – Dimensionless quantity relating lift to fluid density and velocity over an area; Lift-induced drag – Type of aerodynamic resistance against the motion of a wing or other airfoil; Lift-to-drag ratio – Measure of aerodynamic efficiency; Lifting-line theory – Mathematical model to quantify lift; NACA airfoil – Wing shape
In fact, the profile chord is usually chosen as the reference length also for aerodynamic coefficient for wing sections and thin profiles in which the primary target is to maximize the lift coefficient or the lift/drag ratio (i.e. as usual in thin airfoil theory, one would employ the chord Reynolds as the flow speed parameter for comparing ...
Platform angle of attack Coefficients of drag and lift versus angle of attack. Stall speed corresponds to the angle of attack at the maximum coefficient of lift (C LMAX) A typical lift coefficient curve for an airfoil at a given airspeed. The lift coefficient of a fixed-wing aircraft varies with angle of attack. Increasing angle of attack is ...