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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 ...
Because the air at the surface has near-zero velocity but the air away from the surface is moving, there is a thin boundary layer in which air close to the surface is subjected to a shearing motion. [ 72 ] [ 73 ] The air's viscosity resists the shearing, giving rise to a shear stress at the airfoil's surface called skin friction drag .
Isaac Newton's sine-squared law of air resistance is a formula that implies the force on a flat plate immersed in a moving fluid is proportional to the square of the sine of the angle of attack. Although Newton did not analyze the force on a flat plate himself, the techniques he used for spheres, cylinders, and conical bodies were later applied ...
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 Magnus effect is a phenomenon that occurs when a spinning object is moving through a fluid or gas (air). A lift force acts on the spinning object and its path may be deflected in a manner not present when it is not spinning. The strength and direction of the Magnus effect is dependent on the speed and direction of the rotation of the object ...
Traditionally, compressed air work was limited to maximum ambient pressures of between 3 and 4 bars (3.0 and 3.9 atm), but experience with offshore saturation diving shows that higher pressures can be managed at acceptable risk using the techniques developed in that industry, including saturation exposures and the use of breathing gases other than air.
For the precise establishment of drag or air resistance effects on projectiles, Doppler radar measurements are required. Weibel 1000e or Infinition BR-1001 Doppler radars are used by governments, professional ballisticians, defence forces and a few ammunition manufacturers to obtain real-world data of the flight behavior of projectiles of their ...
The model can be used to predict the flutter margin and, if necessary, test fixes to potential problems. Small carefully chosen changes to mass distribution and local structural stiffness can be very effective in solving aeroelastic problems. Methods of predicting flutter in linear structures include the p-method, the k-method and the p-k ...