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Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
The subsonic speed range is that range of speeds within which, all of the airflow over an aircraft is less than Mach 1. The critical Mach number (Mcrit) is lowest free stream Mach number at which airflow over any part of the aircraft first reaches Mach 1. So the subsonic speed range includes all speeds that are less than Mcrit. Transonic: 0.8–1.2
[1] [2] The ISO standard symbol for the knot is kn. [3] The same symbol is preferred by the Institute of Electrical and Electronics Engineers , while kt is also common, especially in aviation, where it is the form recommended by the International Civil Aviation Organization . [4] The knot is a non-SI unit. [5]
TAS can be calculated as a function of Mach number and static air temperature: =, where is the speed of sound at standard sea level (661.47 knots (1,225.04 km/h; 340.29 m/s)),
Ground speed is just a pilot aid to estimate if the flight is on time, behind or ahead of schedule. It is not used for takeoff and landing purposes, since the imperative speed for a flying aircraft always is the speed against the wind. The Machmeter is, on subsonic aircraft, a warning indicator.
Symbol Factor or; yotta Y 10 24: 1 000 000 000 000 000 000 000 000: zetta Z 10 21: 1 000 000 000 000 000 000 000: exa E 10 18: 1 000 000 000 000 000 000: peta P 10 15: 1 000 000 000 000 000: tera T 10 12: 1 000 000 000 000: giga G 10 9: 1 000 000 000: mega M 10 6: 1 000 000: kilo k 10 3: 1 000: hecto h 10 2: 100 deca da 10 1: 10 (none) (none) 1 ...
The upstream Mach number, , begins at 1 and ends at 5. Although the tables could be extended over any range of Mach numbers, stopping at Mach 5 is typical since assuming γ {\displaystyle \gamma } to be 1.4 over the entire Mach number range leads to errors over 10% beyond Mach 5.
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h).