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Impact Pressure
In compressible fluid dynamics, impact pressure ( dynamic pressure) is the difference between total pressure (also known as pitot pressure or stagnation pressure) and static pressure. In aerodynamics notation, this quantity is denoted as q_c or Q_c. When input to an airspeed indicator, impact pressure is used to provide a calibrated airspeed reading. An air data computer with inputs of pitot and static pressures is able to provide a Mach number and, if static temperature is known, true airspeed. Some authors in the field of compressible flows use the term ''dynamic pressure'' or ''compressible dynamic pressure'' instead of ''impact pressure''. L. J. Clancy (1975) ''Aerodynamics'', Section 3.12 and 3.13"the dynamic pressure is equal to ''half rho vee squared'' only in incompressible flow."Houghton, E.L. and Carpenter, P.W. (1993), ''Aerodynamics for Engineering Students'', Section 2.3.1 Isentropic flow In isentropic flow the ratio of total pressure to static pressure is given ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Pressure
In fluid dynamics, dynamic pressure (denoted by or and sometimes called velocity pressure) is the quantity defined by:Clancy, L.J., ''Aerodynamics'', Section 3.5 :q = \frac\rho\, u^2 where (in SI units): * is the dynamic pressure in pascals (i.e., N/ m2), * (Greek letter rho) is the fluid mass density (e.g. in kg/m3), and * is the flow speed in m/s. It can be thought of as the fluid's kinetic energy per unit volume. For incompressible flow, the dynamic pressure of a fluid is the difference between its total pressure and static pressure. From Bernoulli's law, dynamic pressure is given by : p_0 - p_\text = \frac\rho\, u^2 where and are the total and static pressures, respectively. Physical meaning Dynamic pressure is the kinetic energy per unit volume of a fluid. Dynamic pressure is one of the terms of Bernoulli's equation, which can be derived from the conservation of energy for a fluid in motion. At a stagnation point the dynamic pressure is equal to the difference ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pitot Pressure
Pitot pressure is the pressure that can be measured by a Pitot tube, with an open-ended tube facing into the oncoming fluid with the other end closed off. The stationary fluid can be connected to a pressure-measuring device, or used in various devices. For subsonic flow, pitot pressure is equal to the stagnation pressure In fluid dynamics, stagnation pressure, also referred to as total pressure, is what the pressure would be if all the kinetic energy of the fluid were to be converted into pressure in a reversable manner.; it is defined as the sum of the free-strea ... (or total pressure) of the flow, and hence the term pitot pressure is often used interchangeably with these other terms. For supersonic flow, however, pitot pressure is the stagnation pressure of the flow behind the normal shock ahead of the pitot tube. Pitot pressure is named for Henri Pitot, French scientist. References Pressure {{Measurement-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stagnation Pressure
In fluid dynamics, stagnation pressure, also referred to as total pressure, is what the pressure would be if all the kinetic energy of the fluid were to be converted into pressure in a reversable manner.; it is defined as the sum of the free-stream static pressure and the free-stream dynamic pressure. The Bernoulli equation applicable to incompressible flow shows that the stagnation pressure is equal to the dynamic pressure and static pressure combined.Clancy, L.J. (1975), ''Aerodynamics'', Pitman Publishing Limited, London. In compressible flows, stagnation pressure is also equal to total pressure as well, provided that the fluid entering the stagnation point is brought to rest Isentropic flow, isentropically. Stagnation pressure is sometimes referred to as pitot pressure because the two pressures are equal. Magnitude The magnitude of stagnation pressure can be derived from Bernoulli's principle, Bernoulli equation for incompressible flow and no height changes. For any two po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Pressure
In fluid mechanics the term static pressure refers to a term in Bernoulli's equation written words as ''static pressure + dynamic pressure = total pressure''. Since pressure measurements at any single point in a fluid always give the static pressure value, the 'static' is often dropped. In the design and operation of aircraft, ''static pressure'' is the air pressure in the aircraft's static pressure system. Static pressure in fluid dynamics The concept of pressure is central to the study of fluids. A pressure can be identified for every point in a body of fluid, regardless of whether the fluid is in motion. Pressure can be measured using an aneroid, Bourdon tube, mercury column, or various other methods. The concepts of ''total pressure'' and '' dynamic pressure'' arise from Bernoulli's equation and are significant in the study of all fluid flows. These two pressures are not pressures in the usual sense - they cannot be measured using a pressure sensor. To avoid potential ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamics
Aerodynamics () is the study of the motion of atmosphere of Earth, 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, and is an important domain of study in aeronautics. 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 Aircraft#Heavier-than-air – aerodynes, 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 si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calibrated Airspeed
In aviation, calibrated airspeed (CAS) is indicated airspeed corrected for instrument and position error. When flying at sea level under International Standard Atmosphere conditions (15 °C, 1013 hPa, 0% humidity) calibrated airspeed is the same as equivalent airspeed (EAS) and true airspeed (TAS). If there is no wind it is also the same as ground speed (GS). Under any other conditions, CAS may differ from the aircraft's TAS and GS. Calibrated airspeed in knots is usually abbreviated as ''KCAS'', while indicated airspeed is abbreviated as ''KIAS''. In some applications, notably British usage, the expression ''rectified airspeed'' is used instead of calibrated airspeed. Practical applications of CAS CAS has two primary applications in aviation: * for navigation, CAS is traditionally calculated as one of the steps between indicated airspeed and true airspeed; * for aircraft control, CAS (and EAS) are the primary reference points, since they describe the dynamic pressure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Data Computer
An air data computer (ADC) or central air data computer (CADC) computes altitude, vertical speed, air speed, and Mach number from pressure and temperature inputs. It is an essential avionics component found in modern aircraft. This computer, rather than individual flight instruments, instruments, can determine the calibrated airspeed, Mach number, altitude, and vertical speed indicator, altitude trend data from an aircraft's pitot-static system. In some very high-speed aircraft such as the Space Shuttle, equivalent airspeed is calculated instead of calibrated airspeed. Air data computers usually also have an input of total air temperature. This enables the computation of static air temperature and true airspeed. Models In Airbus aircraft the air data computer is combined with attitude, heading and navigation sources in a single unit known as the Air Data Inertial Reference Unit (ADIRU) which has now been replaced by the Global Navigation Air Data Inertial Reference System (GNADI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mach Number
The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. It is named after the Austrian physicist and philosopher Ernst Mach. \mathrm = \frac, where: * is the local Mach number, * is the local flow velocity with respect to the boundaries (either internal, such as an object immersed in the flow, or external, like a channel), and * is the speed of sound in the medium, which in air varies with the square root of the thermodynamic temperature. By definition, at Mach1, the local flow velocity is equal to the speed of sound. At Mach0.65, is 65% of the speed of sound (subsonic), and, at Mach1.35, is 35% faster than the speed of sound (supersonic). The local speed of sound, and hence the Mach number, depends on the temperature of the surrounding gas. The Mach number is primarily used to determine the approximation with which a flow can be treated as an i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
True Airspeed
The true airspeed (TAS; also KTAS, for ''knots true airspeed'') of an aircraft is the speed of the aircraft relative to the air mass through which it is flying. The true airspeed is important information for accurate navigation of an aircraft. Traditionally it is measured using an analogue TAS indicator, but as GPS has become available for civilian use, the importance of such air-measuring instruments has decreased. Since ''indicated'', as opposed to ''true'', airspeed is a better indicator of margin above the stall, true airspeed is not used for controlling the aircraft; for these purposes the indicated airspeed – IAS or KIAS (knots indicated airspeed) – is used. However, since indicated airspeed only shows true speed through the air at standard sea level pressure and temperature, a TAS meter is necessary for navigation purposes at cruising altitude in less dense air. The IAS meter reads very nearly the TAS at lower altitude and at lower speed. On jet airliners the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isentropic Flow
An isentropic process is an idealized thermodynamic process that is both adiabatic and reversible. The work transfers of the system are frictionless, and there is no net transfer of heat or matter. Such an idealized process is useful in engineering as a model of and basis of comparison for real processes. This process is idealized because reversible processes do not occur in reality; thinking of a process as both adiabatic and reversible would show that the initial and final entropies are the same, thus, the reason it is called isentropic (entropy does not change). Thermodynamic processes are named based on the effect they would have on the system (ex. isovolumetric: constant volume, isenthalpic: constant enthalpy). Even though in reality it is not necessarily possible to carry out an isentropic process, some may be approximated as such. The word "isentropic" derives from the process being one in which the entropy of the system remains unchanged. In addition to a process wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Capacity Ratio
In thermal physics and thermodynamics, the heat capacity ratio, also known as the adiabatic index, the ratio of specific heats, or Laplace's coefficient, is the ratio of the heat capacity at constant pressure () to heat capacity at constant volume (). It is sometimes also known as the '' isentropic expansion factor'' and is denoted by (gamma) for an ideal gasγ first appeared in an article by the French mathematician, engineer, and physicist Siméon Denis Poisson: * On p. 332, Poisson defines γ merely as a small deviation from equilibrium which causes small variations of the equilibrium value of the density ρ. In Poisson's article of 1823 – * γ was expressed as a function of density D (p. 8) or of pressure P (p. 9). Meanwhile, in 1816 the French mathematician and physicist Pierre-Simon Laplace had found that the speed of sound depends on the ratio of the specific heats. * However, he didn't denote the ratio as γ. In 1825, Laplace stated that the speed of sound i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binomial Series
In mathematics, the binomial series is a generalization of the binomial formula to cases where the exponent is not a positive integer: where \alpha is any complex number, and the power series on the right-hand side is expressed in terms of the (generalized) binomial coefficients :\binom = \frac. The binomial series is the MacLaurin series for the function f(x)=(1+x)^\alpha. It converges when , x, - 1 is assumed. On the other hand, the series does not converge if , x, =1 and \operatorname(\alpha) \le - 1 , again by formula (). Alternatively, we may observe that for all j, \left, \fracj - 1 \ \ge 1 - \fracj \ge 1 . Thus, by formula (), for all k, \left, \ \ge 1 . This completes the proof of (iii). Turning to (iv), we use identity () above with x=-1 and \alpha-1 in place of \alpha, along with formula (), to obtain :\sum_^n \! (-1)^k = \! (-1)^n= \frac1 (1+o(1)) as n\to\infty. Assertion (iv) now follows from the asymptotic behavior of the sequence n^ = e^. (Precisely, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
