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Betz' Law
Betz's law indicates the maximum power that can be extracted from the wind, independent of the design of a wind turbine in open flow. It was published in 1919 by the German physicist Albert Betz. The law is derived from the principles of conservation of mass and momentum of the air stream flowing through an idealized " actuator disk" that extracts energy from the wind stream. According to Betz's law, no turbine can capture more than 16/27 (59.3%) of the kinetic energy in wind. The factor 16/27 (0.593) is known as Betz's coefficient. Practical utility-scale wind turbines achieve at peak 75–80% of the Betz limit. The Betz limit is based on an open-disk actuator. If a diffuser is used to collect additional wind flow and direct it through the turbine, more energy can be extracted, but the limit still applies to the cross-section of the entire structure. Concepts Betz's law applies to all Newtonian fluids, including wind. If all of the energy coming from wind movement through a t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power (physics)
In physics, power is the amount of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt, equal to one joule per second. In older works, power is sometimes called ''activity''. Power is a scalar quantity. Power is related to other quantities; for example, the power involved in moving a ground vehicle is the product of the aerodynamic drag plus traction force on the wheels, and the velocity of the vehicle. The output power of a motor is the product of the torque that the motor generates and the angular velocity of its output shaft. Likewise, the power dissipated in an electrical element of a circuit is the product of the current flowing through the element and of the voltage across the element. Definition Power is the rate with respect to time at which work is done; it is the time derivative of work: P =\frac where is power, is work, and is time. If a constant force F is applied throughout a distance x, the wor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wind Power
Wind power or wind energy is mostly the use of wind turbines to electricity generation, generate electricity. Wind power is a popular, sustainable energy, sustainable, renewable energy source that has a much smaller Environmental impact of wind power, impact on the environment than burning fossil fuels. Historically, wind power has been used in sails, windmills and windpumps but today it is mostly used to generate electricity. Wind farms consist of many individual wind turbines, which are connected to the electric power transmission Electrical grid, network. New Onshore wind farm, onshore (on-land) wind farms are cheaper than new Coal-fired power station, coal or Gas-fired power plant, gas plants, but expansion of wind power is being hindered by fossil fuel subsidies. Onshore wind farms have a greater visual #Impact on environment and landscape, impact on the landscape than some other power stations. Small onshore wind farms can feed some energy into the grid or provide power t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computational Fluid Dynamics
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid ( liquids and gases) with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems. Ongoing research yields software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows. Initial validation of such software is typically performed using experimental apparatus such as wind tunnels. In addition, previously performed analytical or empirical analysis of a particular problem can be used for comparison. A final validation is often performed using full-scale testing, such as flight tests. CFD is applied to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gustav Kirchhoff
Gustav Robert Kirchhoff (; 12 March 1824 – 17 October 1887) was a German physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects. He coined the term black-body radiation in 1862. Several different sets of concepts are named "Kirchhoff's laws" after him, concerning such diverse subjects as black-body radiation and spectroscopy, electrical circuits, and thermochemistry. The Bunsen–Kirchhoff Award for spectroscopy is named after him and his colleague, Robert Bunsen. Life and work Gustav Kirchhoff was born on 12 March 1824 in Königsberg, Prussia, the son of Friedrich Kirchhoff, a lawyer, and Johanna Henriette Wittke. His family were Lutherans in the Evangelical Church of Prussia. He graduated from the Albertus University of Königsberg in 1847 where he attended the mathematico-physical seminar directed by Carl Gustav Jacob Jacobi, Franz Ernst Neumann and Friedrich Julius Ri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alexander Gorlov
Alexander M. Gorlov (March 23, 1931 – June 10, 2016) was a Russian mechanical engineer who was Professor Emeritus and Director of Hydro-Pneumatic Power Laboratory at Northeastern University in Boston, Massachusetts. Early life Alexander M. Gorlov was born into the family of a prosperous lawyer. His father was arrested and died in prison during Joseph Stalin's purges. His mother also spent a number of years in concentration camps in Russia, which forced young Alexander Gorlov to spend some of his childhood years in the orphanage in a remote Russian Urals area. Gorlov received his Doctorate in engineering and had a successful scientific career in Moscow for a number of years during the relatively liberal period of the so-called Khrushchev Thaw. He was granted the Gold and two Bronze Medals for Achievements of the USSR National Economy. In 1975 because of his friendship with Alexander Solzhenitsyn, the Nobel Prize winner and outspoken critic of the communist system, Gorlov was fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alexander Nikolaevich Gorban
Alexander Nikolaevich Gorban (russian: Александр Николаевич Горба́нь) is a scientist of Russian origin, working in the United Kingdom. He is a professor at the University of Leicester, and director of its Mathematical Modeling Centre. Gorban has contributed to many areas of fundamental and applied science, including statistical physics, non-equilibrium thermodynamics, machine learning and mathematical biology. Gorban is the author of about 20 books and 300 scientific publications. He has founded several scientific schools in the areas of physical and chemical kinetics, dynamical systems theory and artificial neural networks, and is ranked as one of the 1000 most cited researchers of Russian origin.According to http://www.scientific.ru/ , 2012 Gorban has supervised 6 habilitations and more than 30 PhD theses. Biography Alexander N. Gorban was born in Omsk on 19 April 1952. His father Nikolai Vasilievich Gorban was a historian and writer exiled to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermann Glauert
Hermann Glauert, Fellow of the Royal Society, FRS (4 October 1892 – 6 August 1934) was a British aerodynamicist and Principal Scientific Officer of the Royal Aircraft Establishment, Farnborough, Hampshire, Farnborough until his death in 1934 in aviation, 1934. Early life and education Glauert was born in Sheffield, Yorkshire; his father Louis Glauert was a cutlery manufacturer. He attended King Edward VII School (Sheffield), King Edward VII School, Sheffield and Trinity College, Cambridge. Career Glauert wrote numerous reports and memoranda dealing with aerofoil and propeller (aircraft), propeller theory. His book, ''The Elements of Aerofoil and Airscrew Theory'' was the single most important instrument for spreading airfoil and wing theory around the English speaking world. Glauert independently developed Prandtl-Glauert method from the then-existing aerodynamic theory and published his results in ''Royal Society, The Proceedings of the Royal Society'' in 1928. In the 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wind-powered Vehicle
Wind-powered vehicles derive their power from sails, kites or rotors and ride on wheels—which may be linked to a wind-powered rotor—or runners. Whether powered by sail, kite or rotor, these vehicles share a common trait: As the vehicle increases in speed, the advancing airfoil encounters an increasing apparent wind at an angle of attack that is increasingly smaller. At the same time, such vehicles are subject to relatively low forward resistance, compared with traditional sailing craft. As a result, such vehicles are often capable of speeds exceeding that of the wind. Rotor-powered examples have demonstrated ground speeds that exceed that of the wind, both directly ''into the wind'' and directly ''downwind'' by transferring power through a drive train between the rotor and the wheels. The wind-powered speed record is by a vehicle with a sail on it, ''Greenbird'', with a recorded top speed of . Other wind-powered conveyances include sailing vessels that travel on water, and bal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Derivative
In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. For example, the derivative of the position of a moving object with respect to time is the object's velocity: this measures how quickly the position of the object changes when time advances. The derivative of a function of a single variable at a chosen input value, when it exists, is the slope of the tangent line to the graph of the function at that point. The tangent line is the best linear approximation of the function near that input value. For this reason, the derivative is often described as the "instantaneous rate of change", the ratio of the instantaneous change in the dependent variable to that of the independent variable. Derivatives can be generalized to functions of several real variables. In this generalization, the derivativ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ratio
In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ratio 4:3). Similarly, the ratio of lemons to oranges is 6:8 (or 3:4) and the ratio of oranges to the total amount of fruit is 8:14 (or 4:7). The numbers in a ratio may be quantities of any kind, such as counts of people or objects, or such as measurements of lengths, weights, time, etc. In most contexts, both numbers are restricted to be Positive integer, positive. A ratio may be specified either by giving both constituting numbers, written as "''a'' to ''b''" or "''a'':''b''", or by giving just the value of their quotient Equal quotients correspond to equal ratios. Consequently, a ratio may be considered as an ordered pair of numbers, a Fraction (mathematics), fraction with the first number in the numerator and the second in the denom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Flow Rate
In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Its unit is kilogram per second in SI units, and slug per second or pound per second in US customary units. The common symbol is \dot (''ṁ'', pronounced "m-dot"), although sometimes ''μ'' (Greek lowercase mu) is used. Sometimes, mass flow rate is termed ''mass flux'' or ''mass current'', see for example ''Schaum's Outline of Fluid Mechanics''. In this article, the (more intuitive) definition is used. Mass flow rate is defined by the limit: \dot = \lim_ \frac = \frac i.e., the flow of mass through a surface per unit time . The overdot on the is Newton's notation for a time derivative. Since mass is a scalar quantity, the mass flow rate (the time derivative of mass) is also a scalar quantity. The change in mass is the amount that flows ''after'' crossing the boundary for some time duration, not the initial amount of mass at the boundary minus the final amount at the boun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
