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A different area rule, known as the supersonic area rule, developed by NACA aerodynamicist Robert Jones in "Theory of wing-body drag at supersonic speeds", [2] is applicable at speeds beyond transonic, and in this case, the cross-sectional area requirement is established with relation to the angle of the Mach cone for the design speed.
The H/V curve also contains a take-off profile, indicating how a pilot can start from 0 height and 0 speed, and safely traverse to cruise. At low heights with low airspeed, such as a hover taxi, the pilot can simply cushion the landing with collective by converting rotational inertia into lift. Conversely, a complete power loss, and resultant ...
These vary with speed, so the results are typically plotted on a 2-dimensional graph. In almost all cases the graph forms a U-shape, due to the two main components of drag. The L/D may be calculated using computational fluid dynamics or computer simulation. It is measured empirically by testing in a wind tunnel or in free flight test. [1] [2] [3]
[1] [2] [3] The Kármán–Moore theory indicates that the wave drag scales as the square of the second derivative of the area distribution, [″ ()] (see full expression below), so for low wave drag it is necessary that () be smooth. Thus, the Sears–Haack body is pointed at each end and grows smoothly to a maximum and then decreases smoothly ...
The low speed region of flight is known as the "back of the power curve" or "behind the power curve" [7] [8] (sometimes "back of the drag curve") where more thrust is required to sustain flight at lower speeds. It is an inefficient region of flight because a decrease in speed requires increased thrust and a resultant increase in fuel consumption.
In practice a rough un-streamlined body (a bluff body) will have a around 1, more or less. Smoother objects can have much lower values of c d {\displaystyle c_{\rm {d}}} . The equation is precise – it simply provides the definition of c d {\displaystyle c_{\rm {d}}} ( drag coefficient ), which varies with the Reynolds number and is found by ...
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The beam is originally straight, and any taper is slight; The beam experiences only linear elastic deformation; The beam is slender (its length to height ratio is greater than 10) Only small deflections are considered (max deflection less than 1/10 of the span).