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In aerodynamics, aerodynamic drag, also known as air resistance, is the fluid drag force that acts on any moving solid body in the direction of the air's freestream flow. [ 22 ] From the body's perspective (near-field approach), the drag results from forces due to pressure distributions over the body surface, symbolized D p r {\displaystyle D ...
is the resistance (atkinsons), is the rate of flow of air (thousands of cubic feet per second). 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.
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.
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.
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.
Year 7 is an educational year group in schools in many countries including England, Wales, Australia and New Zealand. It is the seventh full year (or eighth in Australia and England) of compulsory education and is roughly equivalent to grade 6 in the United States and Canada (or to grade 7 for the Australian Year 7). Children in this year are ...
It can be successfully applied to air flow in lung alveoli, or the flow through a drinking straw or through a hypodermic needle. It was experimentally derived independently by Jean Léonard Marie Poiseuille in 1838 [ 1 ] and Gotthilf Heinrich Ludwig Hagen , [ 2 ] and published by Hagen in 1839 [ 1 ] and then by Poiseuille in 1840–41 and 1846 ...
An aerostat (from Ancient Greek ἀήρ (aḗr) ' air ' and στατός (statós) ' standing ', via French) or lighter-than-air aircraft is an aircraft that relies on buoyancy to maintain flight. Aerostats include the unpowered balloons (free-flying or tethered ) and the powered airships .