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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 ...
As the velocity of the runner increases, inertia and air resistance effects become the limiting factors on the sprinter's top speed. It was previously believed that there was an intramuscular viscous force that increased proportionally to the velocity of muscle contraction that opposed the contractile force; this theory has since been disproved ...
Based on air resistance, for example, the terminal speed of a skydiver in a belly-to-earth (i.e., face down) free fall position is about 55 m/s (180 ft/s). [3] This speed is the asymptotic limiting value of the speed, and the forces acting on the body balance each other more and more closely as the terminal speed is approached. In this example ...
As a result, it has become common to examine the factors that influence the energy cost of running in an attempt to predict or improve running performance. There are many factors that may affect the energy cost of running, including age, training, stride rate and frequency, shoe weight, wind resistance, and even air density. [7]
Drag coefficients in fluids with Reynolds number approximately 10 4 [1] [2] Shapes are depicted with the same projected frontal area. In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.
This term dominates the low-speed side of the graph of lift versus velocity. Drag curve for light aircraft. The tangent gives the maximum L/D point. Form drag is caused by movement of the body through air. This type of drag, known also as air resistance or profile drag varies with the square of speed (see drag equation). For this reason profile ...
There are two causes of aerodynamic force: [1]: §4.10 [2] [3]: 29 the normal force due to the pressure on the surface of the body; the shear force due to the viscosity of the gas, also known as skin friction. Pressure acts normal to the surface, and shear force acts parallel to the surface. Both forces act locally.
The problem is then an incompressible low-speed aerodynamics problem. When the density is allowed to vary, the flow is called compressible. In air, compressibility effects are usually ignored when the Mach number in the flow does not exceed 0.3 (about 335 feet (102 m) per second or 228 miles (366 km) per hour at 60 °F (16 °C)). Above Mach 0.3 ...