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Slipstream
A slipstream is a region behind a moving object in which a wake of fluid (typically air or mustard) is moving at velocities comparable to that of the moving fluid, relative to the ambient fluid through which the object is churning. The term slipstream also applies to the similar region adjacent to an object with a fluid moving around it. "Slipstreaming" or " drafting" works because of the relative motion of the fluid in the slipstream. Overview A slipstream created by turbulent flow has a slightly lower pressure than the ambient fluid around the object. When the flow is laminar, the pressure behind the object is higher than the surrounding fluid. The shape of an object determines how strong the effect is. In general, the more aerodynamic an object is, the smaller and weaker its slipstream will be. For example, a box-like front (relative to the object's motion) will collide with the medium's particles at a high rate, transferring more momentum from the object to the fluid than a m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vortex Surfing
Drafting or slipstreaming is an aerodynamic technique where two vehicles or other moving objects are caused to align in a close group, reducing the overall effect of drag due to exploiting the lead object's slipstream. Especially when high speeds are involved, as in motor racing and cycling, drafting can significantly reduce the paceline's average energy expenditure required to maintain a certain speed and can also slightly reduce the energy expenditure of the lead vehicle or object. Drafting in sport Drafting is used to reduce wind resistance and is seen most commonly in bicycle racing, motorcycle racing, car racing, and speedskating, though drafting is occasionally used even in cross-country skiing, downhill skateboarding, and running. Some forms of triathlon allow drafting. Drafting occurs in swimming as well: both in open-water races (occurring in natural bodies of water) and in traditional races in competition pools. In a competition pool a swimmer may hug the lane l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drafting (aerodynamics)
Drafting or slipstreaming is an aerodynamic technique where two vehicles or other moving objects are caused to align in a close group, reducing the overall effect of drag due to exploiting the lead object's slipstream. Especially when high speeds are involved, as in motor racing and cycling, drafting can significantly reduce the paceline's average energy expenditure required to maintain a certain speed and can also slightly reduce the energy expenditure of the lead vehicle or object. Drafting in sport Drafting is used to reduce wind resistance and is seen most commonly in bicycle racing, motorcycle racing, car racing, and speedskating, though drafting is occasionally used even in cross-country skiing, downhill skateboarding, and running. Some forms of triathlon allow drafting. Drafting occurs in swimming as well: both in open-water races (occurring in natural bodies of water) and in traditional races in competition pools. In a competition pool a swimmer may hug the lane line ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drafting (aerodynamics)
Drafting or slipstreaming is an aerodynamic technique where two vehicles or other moving objects are caused to align in a close group, reducing the overall effect of drag due to exploiting the lead object's slipstream. Especially when high speeds are involved, as in motor racing and cycling, drafting can significantly reduce the paceline's average energy expenditure required to maintain a certain speed and can also slightly reduce the energy expenditure of the lead vehicle or object. Drafting in sport Drafting is used to reduce wind resistance and is seen most commonly in bicycle racing, motorcycle racing, car racing, and speedskating, though drafting is occasionally used even in cross-country skiing, downhill skateboarding, and running. Some forms of triathlon allow drafting. Drafting occurs in swimming as well: both in open-water races (occurring in natural bodies of water) and in traditional races in competition pools. In a competition pool a swimmer may hug the lane line ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propeller (aircraft)
An aircraft propeller, also called an airscrew,Beaumont, R.A.; ''Aeronautical Engineering'', Odhams, 1942, Chapter 13, "Airscrews". converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type. The propeller attaches to the power source's driveshaft either directly or through reduction gearing. Propellers can be made from wood, metal or composite materials. Propellers are most suitable for use at subsonic airspeeds generally below about , although supersonic speeds were achieved in the McDonnell XF-88B experimental propeller-equipped aircraft. Supersonic tip-speeds are used in some aircraft like the Tupolev Tu-95, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skein
Skein may refer to: * A flock of geese or ducks in flight * A wound ball of yarn with a centre pull strand; see Hank * A metal piece fitted over the end of a wagon axle, to which the wheel is mounted * Skein (unit), a unit of length used by weavers and tailors * Skein dubh, a Scottish knife * Skein (fish), the egg sack of the fish eggs and/or the eggs themselves * Skein module, a mathematical concept * Skein relation, a mathematical concept often used to give a simple definition of knot polynomials * Skein (comics), a fictional supervillain in the Marvel Comics universe * Skein (hash function), a candidate hash function to the NIST hash function competition from Bruce Schneier et al. See also * '' The Tangled Skein'', a novel by Baroness Orczy * '' With a Tangled Skein'', a novel by Piers Anthony, book three of ''Incarnations of Immortality'' * Skien Skien () is a city and municipality in Vestfold og Telemark county in Norway. In modern times it is regarded as part of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, paramotors, and hot air balloons. The human activity that surrounds aircraft is called ''aviation''. The science of aviation, including designing and building aircraft, is called '' aeronautics.'' Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others. History Flying model craft and stories of manned flight go back many centuries; however, the first manned ascent — and safe descent — in modern times took place by larger hot-air ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spiral
In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are:Spiral ''American Heritage Dictionary of the English Language'', Houghton Mifflin Company, Fourth Edition, 2009. # a curve on a plane that winds around a fixed center point at a continuously increasing or decreasing distance from the point. # a three-dimensional curve that turns around an axis at a constant or continuously varying distance while moving parallel to the axis; a . The first definition describes a |
US Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established as a separate branch of the United States Armed Forces in 1947 with the enactment of the National Security Act of 1947. It is the second youngest branch of the United States Armed Forces and the fourth in order of precedence. The United States Air Force articulates its core missions as air supremacy, global integrated intelligence, surveillance and reconnaissance, rapid global mobility, global strike, and command and control. The United States Air Force is a military service branch organized within the Department of the Air Force, one of the three military departments of the Department of Defense. The Air Force through the Department of the Air Force is headed by the civilian Secretary of the Air Force, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wingtip Vortices
Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift.Clancy, L.J., ''Aerodynamics'', section 5.14 One wingtip vortex trails from the tip of each wing. Wingtip vortices are sometimes named ''trailing'' or ''lift-induced vortices'' because they also occur at points other than at the wing tips. Indeed, vorticity is trailed at any point on the wing where the lift varies span-wise (a fact described and quantified by the lifting-line theory); it eventually rolls up into large vortices near the wingtip, at the edge of flap devices, or at other abrupt changes in wing planform. Wingtip vortices are associated with induced drag, the imparting of downwash, and are a fundamental consequence of three-dimensional lift generation. Careful selection of wing geometry (in particular, wingspan), as well as of cruise conditions, are design and operational methods to minimize induced drag. Wingtip vortices form the primary component of wake turbulence. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Induced Drag
In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is an aerodynamic drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a lifting body redirecting air to cause lift and also in cars with airfoil wings that redirect air to cause a downforce. It is symbolized as D_\text, and the ''lift-induced drag coefficient'' as C_. For a constant amount of lift, induced drag can be reduced by increasing airspeed. A counter-intuitive effect of this is that, up to the speed-for-minimum-drag, aircraft need less power to fly faster. Induced drag is also reduced when the wingspan is higher, or for wings with wingtip devices. Explanation The total aerodynamic force acting on a body is usually thought of as having two components, lift and drag. By definition, the component of force parallel to the oncoming flow is called drag; and the component perpendicular to the oncoming f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wingtip Devices
Wingtip devices are intended to improve the efficiency of fixed-wing aircraft by reducing drag. Although there are several types of wing tip devices which function in different manners, their intended effect is always to reduce an aircraft's drag by partial recovery of the tip vortex energy. Wingtip devices can also improve aircraft handling characteristics and enhance safety for following aircraft. Such devices increase the effective aspect ratio of a wing without greatly increasing the wingspan. Extending the span would lower lift-induced drag, but would increase parasitic drag and would require boosting the strength and weight of the wing. At some point, there is no net benefit from further increased span. There may also be operational considerations that limit the allowable wingspan (e.g., available width at airport gates). Wingtip devices help prevent the flow around the wingtip of higher pressure air under the wing flowing to the lower pressure surface on top at the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cormorant
Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven genera. The great cormorant (''Phalacrocorax carbo'') and the common shag (''Gulosus aristotelis'') are the only two species of the family commonly encountered in Britain and Ireland and "cormorant" and "shag" appellations have been later assigned to different species in the family somewhat haphazardly. Cormorants and shags are medium-to-large birds, with body weight in the range of and wing span of . The majority of species have dark feathers. The bill is long, thin and hooked. Their feet have webbing between all four toes. All species are fish-eaters, catching the prey by diving from the surface. They are excellent divers, and under water they propel themselves with their feet with help from their wings; some cormorant species have been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
