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Natural Laminar Flow
Boundary layer control refers to methods of controlling the behaviour of fluid flow boundary layers. It may be desirable to reduce flow separation on fast vehicles to reduce the size of the wake (streamlining), which may reduce drag. Boundary layer separation is generally undesirable in aircraft high lift coefficient systems and jet engine intakes. Laminar flow produces less skin friction than turbulent but a turbulent boundary layer transfers heat better. Turbulent boundary layers are more resistant to separation. The energy in a boundary layer may need to be increased to keep it attached to its surface. Fresh air can be introduced through slots or mixed in from above. The low momentum layer at the surface can be sucked away through a perforated surface or bled away when it is in a high pressure duct. It can be scooped off completely by a diverter or internal bleed ducting. Its energy can be increased above that of the free stream by introducing high velocity air. Nature Fra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluid Dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation. Fluid dynamics offers a systematic structure—which underlies these practical disciplines—that embraces empirical and semi-empirical laws derived from flow measurement and used to solve practical problems. The solution to a fluid dynamics problem typically involves the calculation of various properties of the fluid, such as flow velocity, pressure, density, and temperature, as functions of space and ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Search And Rescue
Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search is conducted over. These include mountain rescue; ground search and rescue, including the use of search and rescue dogs; urban search and rescue in cities; combat search and rescue on the battlefield and air-sea rescue over water. International Search and Rescue Advisory Group (INSARAG) is a UN organization that promotes the exchange of information between national urban search and rescue organizations. The duty to render assistance is covered by Article 98 of the UNCLOS. Definitions There are many different definitions of search and rescue, depending on the agency involved and country in question. *Canadian Forces: "Search and Rescue comprises the search for, and provision of aid to, persons, ships or other craft which are, or a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turbulator
A turbulator is a device that turns a laminar boundary layer into a turbulent boundary layer. Device Turbulent flow can be desired on parts of the surface of an aircraft wing ( airfoil) or in industrial applications such as heat exchangers and the mixing of fluids. The term “turbulator” is applied to a variety of applications and is used as a derivative of the word turbulent. However, the word has no commonly accepted technical or scientific meaning. It has been approved as a trademark in the U.S. and other countries in conjunction with machine parts used within rotating drums, sterilizers, heat transfer ovens, mixing and pelletizing machines, and air destratification fans for horticultural and agricultural uses, among others. In gliders the turbulator is often a thin zig-zag strip that is placed on the lower side of the wing and sometimes on the vertical stabilizer. In wind sensors ( anemometers), the use of turbulators reduces inaccuracies in the measurement of wind s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamics
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dynamics and its subfield of gas dynamics. The term ''aerodynamics'' is often used synonymously with gas dynamics, the difference being that "gas dynamics" applies to the study of the motion of all gases, and is not limited to air. The formal study of aerodynamics began in the modern sense in the eighteenth century, although observations of fundamental concepts such as aerodynamic drag were recorded much earlier. Most of the early efforts in aerodynamics were directed toward achieving heavier-than-air flight, which was first demonstrated by Otto Lilienthal in 1891. Since then, the use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer simulations has formed a rational basis fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vortex Generator
A vortex generator (VG) is an aerodynamic device, consisting of a small vane usually attached to a lifting surface (or airfoil, such as an aircraft wing) or a rotor blade of a wind turbine.Wind Turbine Vortex Generators UpWind Solutions. VGs may also be attached to some part of an aerodynamic vehicle such as an aircraft fuselage or a car. When the airfoil or the body is in motion relative to the air, the VG creates a ,Peppler, I.L.: ''From The Ground Up'', page 23. Aviation Publishers Co. Limited, Ottawa Ontario, Twenty Seventh Revised Edition, 1996. which, by removing some part of the slow-moving bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boundary Layer Suction
Boundary layer suction is a boundary layer control technique in which an air pump is used to extract the boundary layer at the wing or the inlet of an aircraft. Improving the air flow can reduce drag. Improvements in fuel efficiency have been estimated as high as 30%. The boundary layer The air molecules at the surface of a wing are effectively stationary (see the no-slip condition). If the flow is smooth, known as laminar flow, the velocity of the air increases steadily as measurements are taken further away from the surface. However the smooth flow is often disturbed by the boundary layer breaking away from the surface and creating a low pressure region immediately behind the airfoil (see flow separation). This low pressure region results in increased overall drag. Attempts have been made over the years to delay the onset of this flow separation by careful design and smooth surfaces. Use of suction As flow separation results from the velocity deficit that is characteristic of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leading Edge Slot
A leading-edge slot is a fixed aerodynamic feature of the wing of some aircraft to reduce the stall speed and promote good low-speed handling qualities. A leading-edge slot is a spanwise gap in each wing, allowing air to flow from below the wing to its upper surface. In this manner they allow flight at higher angles of attack and thus reduce the stall speed. Purpose and development At an angle of attack above about 15° many airfoils enter the stall. Modification of such an airfoil with a fixed leading-edge slot can increase the stalling angle to between 22° and 25°.Clancy, L.J., ''Aerodynamics'', Section 6.9 Slots were first developed by Handley Page in 1919 and the first aircraft to fly with them was the experimental H.P.17, a modified Airco DH.9A. Their invention is credited jointly to Sir Frederick Handley Page and Gustav Lachmann. The first aircraft fitted with controllable slots was the Handley Page H.P.20. Licensing the design became one of Handley Page's majo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circulation Control Wing
A circulation control wing (CCW) is a form of high-lift device for use on the main wing of an aircraft to increase the maximum lift coefficient. CCW technology has been in the research and development phase for over sixty years. Blown flaps were an early example of CCW. The CCW works by increasing the velocity of the airflow over the leading edge and trailing edge of a specially designed aircraft wing using a series of blowing slots that eject jets of high-pressure air. The wing has a rounded trailing edge to tangentially eject the air through the Coandă effect thus causing lift. The increase in velocity of the airflow over the wing also adds to the lift force through conventional airfoil lift production. Purpose The main purpose of the circulation control wing is to increase the lifting force of an aircraft at times when large lifting forces at low speeds are required, such as takeoff and landing. Wing flaps and slats are currently used during landing on almost all ai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-lift Device
In aircraft design and aerospace engineering, a high-lift device is a component or mechanism on an aircraft's wing that increases the amount of lift produced by the wing. The device may be a fixed component, or a movable mechanism which is deployed when required. Common movable high-lift devices include wing flaps and slats. Fixed devices include leading-edge slots, leading edge root extensions, and boundary layer control systems. Purpose The size and lifting capacity of a fixed wing is chosen as a compromise between differing requirements. For example, a larger wing will provide more lift and reduce the distance and speeds required for takeoff and landing, but will increase drag, which reduces performance during the cruising portion of flight. Modern passenger jet wing designs are optimized for speed and efficiency during the cruise portion of flight, since this is where the aircraft spends the vast majority of its flight time. High-lift devices compensate for this design ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coandă Effect
The Coandă effect ( or ) is the tendency of a fluid jet to stay attached to a convex surface. ''Merriam-Webster'' describes it as "the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to entrain fluid from the surroundings so that a region of lower pressure develops." It is named after Romanian inventor Henri Coandă, who was the first to recognize the practical application of the phenomenon in aircraft design around 1910. It was first documented explicitly in two patents issued in 1936. Discovery An early description of this phenomenon was provided by Thomas Young in a lecture given to The Royal Society in 1800: A hundred years later, Henri Coandă identified an application of the effect during experiments with his Coandă-1910 aircraft, which mounted an unusual engine he designed. The motor-driven turbine pushed hot air rearward, and Coandă noticed that the airflow was attracted to nearby surfaces. In 1934 Coandă ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blown Flap
Blown flaps, or jet flaps, are powered aerodynamic high-lift devices used on the wings of certain aircraft to improve their low-speed flight characteristics. They use air blown through nozzles to shape the airflow over the rear edge of the wing, directing the flow downward to increase the lift coefficient. There are a variety of methods to achieve this airflow, most of which use jet exhaust or high-pressure air bled off of a jet engine's compressor and then redirected to follow the line of trailing-edge flaps. ''Blown flaps'' may refer specifically to those systems that use internal ductwork within the wing to direct the airflow, or more broadly to systems like upper surface blowing or nozzle systems on conventional underwing engine that direct air through the flaps. Blown flaps are one solution among a broader category known as powered lift, which also includes various boundary layer control systems, systems using directed prop wash, and circulation control wings. Internal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ShinMaywa US-2
The ShinMaywa US-2 is a large Japanese short takeoff and landing amphibious aircraft developed and manufactured by seaplane specialist ShinMaywa (formerly ''Shin Meiwa''). It was developed from the earlier Shin Meiwa US-1A seaplane, which was introduced during the 1970s. The ShinMaywa US-2 was developed on behalf of the Japan Maritime Self-Defense Force (JMSDF) as a 'like-for-like' replacement for its aging US-1A fleet. In Japanese service, it is operated in the air-sea rescue (ASR) role. The US-2 can also be used in other capacities, such as an aerial fire fighter, carrying 15 tonnes of water for this mission. Various overseas operators have held discussions on potential acquisitions of the type, including the Indian Navy and Indian Coast Guard. Other countries such as the United States, Indonesia, Thailand, and Greece have also shown interest in the US-2 for various purposes. Design and development During 1969, the Japan Maritime Self-Defense Force (JMSDF) issued a produ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
