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It is a measure used when comparing the drag of different aircraft. For example, the Douglas DC-3 has an equivalent parasite area of 2.20 m 2 (23.7 sq ft) and the McDonnell Douglas DC-9, with 30 years of advancement in aircraft design, an area of 1.91 m 2 (20.6 sq ft) although it carried five times as many passengers. [10]
Where air is flowing in a laminar manner it has less resistance than when it is flowing in a turbulent manner. If flow becomes turbulent, and the pressure difference is increased to maintain flow, this response itself increases resistance. This means that a large increase in pressure difference is required to maintain flow if it becomes turbulent.
One atkinson is defined as the resistance of an airway which, when air flows along it at a rate of 1,000 cubic feet per second, causes a pressure drop of one pound-force per square foot. The unit is named after J J Atkinson, who published one of the earliest comprehensive mathematical treatments of mine ventilation.
where is resistance at temperature . Therefore, many materials that produce acceptable values of R 0 {\displaystyle R_{0}} include materials that have been alloyed or possess variable negative temperature coefficient (NTC), which occurs when a physical property (such as thermal conductivity or electrical resistivity ) of a material lowers with ...
For medium to longer ranges and flight times, besides gravity, air resistance and wind, several intermediate or meso variables described in the external factors paragraph have to be taken into account for small arms. Meso variables can become significant for firearms users that have to deal with angled shot scenarios or extended ranges, but are ...
Atkinson friction factor is a measure of the resistance to airflow of a duct. It is widely used in the mine ventilation industry but is rarely referred to outside of it. Atkinson friction factor is represented by the symbol k {\displaystyle k} and has the same units as air density (kilograms per cubic metre in SI units , lbfmin^2/ft^4 in ...
A ping pong ball is held in a diagonal stream of air. This is a demonstration of the Coandă effect. The ball "sticks" to the lower side of the air stream, which stops the ball from falling down. The jet as a whole keeps the ball some distance from the jet exhaust, and gravity prevents it from being blown away.
The drag force can also be specified as where P D is the pressure exerted by the fluid on area A.Here the pressure P D is referred to as dynamic pressure due to the kinetic energy of the fluid experiencing relative flow velocity u.