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Prandtl
Ludwig Prandtl (4 February 1875 – 15 August 1953) was a German Fluid mechanics, fluid dynamicist, physicist and aerospace scientist. He was a pioneer in the development of rigorous systematic mathematical analyses which he used for underlying the science of aerodynamics, which have come to form the basis of the applied science of aeronautical engineering. In the 1920s, he developed the mathematical basis for the fundamental principles of Subsonic flight, subsonic aerodynamics in particular; and in general up to and including transonic velocities. His studies identified the boundary layer, thin-Airfoil, airfoils, and Lifting-line theory, lifting-line theories. The Prandtl number was named after him. Early years Prandtl was born in Freising, near Munich, on 4 February 1875. His mother suffered from a lengthy illness and, as a result, Ludwig spent more time with his father, a professor of engineering. His father also encouraged him to observe nature and think about his observati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boundary Layer
In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a Boundary (thermodynamic), bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a No-slip condition, no-slip boundary condition (zero velocity at the wall). The flow velocity then monotonically increases above the surface until it returns to the bulk flow velocity. The thin layer consisting of fluid whose velocity has not yet returned to the bulk flow velocity is called the velocity boundary layer. The air next to a human is heated, resulting in gravity-induced convective airflow, which results in both a velocity and thermal boundary layer. A breeze disrupts the boundary layer, and hair and clothing protect it, making the human feel cooler or warmer. On an aircraft wing, the velocity boundary layer is the part of the flow close to the wing, where viscosity, viscous forces distort the surrounding non-viscous flow. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prandtl Number
The Prandtl number (Pr) or Prandtl group is a dimensionless number, named after the German physicist Ludwig Prandtl, defined as the ratio of momentum diffusivity to thermal diffusivity. The Prandtl number is given as:where: * \nu : momentum diffusivity ( kinematic viscosity), \nu = \mu/\rho, ( SI units: m2/s) * \alpha : thermal diffusivity, \alpha = k/(\rho c_p), (SI units: m2/s) * \mu : dynamic viscosity, (SI units: Pa s = N s/m2) * k : thermal conductivity, (SI units: W/(m·K)) * c_p : specific heat, (SI units: J/(kg·K)) * \rho : density, (SI units: kg/m3). Note that whereas the Reynolds number and Grashof number are subscripted with a scale variable, the Prandtl number contains no such length scale and is dependent only on the fluid and the fluid state. The Prandtl number is often found in property tables alongside other properties such as viscosity and thermal conductivity. The mass transfer analog of the Prandtl number is the Schmidt number and the ratio of the Pran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Closed Wing
A closed wing is a wing that effectively has two main planes that merge at their ends so that there are no conventional wing tips. Closed Wing configuration, wing designs include the annular wing (commonly known as the cylindrical or ring wing), the joined wing, the box wing, and spiroid tip devices. Like many wingtip devices, the closed wing aims to reduce the wasteful effects associated with wingtip vortices that occur at the tips of conventional wings. Although the closed wing has no unique claim on such benefits, many closed wing designs do offer structural advantages over a conventional cantilever wing, cantilever monoplane. Characteristics Wingtip vortices form a major component of wake turbulence and are associated with induced drag, which is a significant contributor to total drag in most regimes. A closed wing avoids the need for wingtips and thus might be expected to reduce wingtip drag (physics), drag effects. In addition to potential structural advantages over open ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane Analogy
The elastic membrane analogy, also known as the soap-film analogy, was first published by pioneering aerodynamicist Ludwig Prandtl in 1903. It describes the stress distribution on a long bar in torsion. The cross section of the bar is constant along its length, and need not be circular. The differential equation that governs the stress distribution on the bar in torsion is of the same form as the equation governing the shape of a membrane under differential pressure. Therefore, in order to discover the stress distribution on the bar, all one has to do is cut the shape of the cross section out of a piece of wood, cover it with a soap film, and apply a differential pressure across it. Then the slope of the soap film at any area of the cross section is directly proportional to the stress in the bar at the same point on its cross section. Application to thin-walled, open cross sections While the membrane analogy allows the stress distribution on any cross section to be determine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lifting-line Theory
The Lanchester–Prandtl lifting-line theoryAnderson, John D. (2001), ''Fundamentals of Aerodynamics'', p. 360. McGraw-Hill, Boston. . is a mathematical model in aerodynamics that predicts lift distribution over a three-dimensional wing from the wing's geometry. The theory was expressed independently by Frederick W. Lanchester in 1907, and by Ludwig Prandtl in 1918–1919 after working with Albert Betz and Max Munk. In this model, the vortex bound to the wing develops along the whole wingspan because it is shed as a vortex-sheet from the trailing edge, rather than just as a single vortex from the wing-tips. Introduction It is difficult to predict analytically the overall amount of lift that a wing of given geometry will generate. When analyzing a three-dimensional finite wing, a traditional approach slices the wing into cross-sections and analyzes each cross-section independently as a wing in a two-dimensional world. Each of these slices is called an airfoil, and it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mixing Length Model
In fluid dynamics, the mixing length model is a method attempting to describe momentum transfer by turbulence Reynolds stresses within a Newtonian fluid boundary layer by means of an eddy viscosity. The model was developed by Ludwig Prandtl in the early 20th century. Prandtl himself had reservations about the model, describing it as, "only a rough approximation," but it has been used in numerous fields ever since, including atmospheric science, oceanography and stellar structure. Also, Ali and Dey hypothesized an advanced concept of mixing instability. Physical intuition The mixing length is conceptually analogous to the concept of mean free path in thermodynamics: a fluid parcel will conserve its properties for a characteristic length, \ \xi' , before mixing with the surrounding fluid. Prandtl described that the mixing length, In the figure above, temperature, \ T, is conserved for a certain distance as a parcel moves across a temperature gradient. The fluctuation in tempe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodore Von Kármán
Theodore von Kármán ( , May 11, 1881May 6, 1963) was a Hungarian-American mathematician, aerospace engineer, and physicist who worked in aeronautics and astronautics. He was responsible for crucial advances in aerodynamics characterizing supersonic and hypersonic airflow. The human-defined threshold of outer space is named the " Kármán line" in recognition of his work. Kármán is regarded as an outstanding aerodynamic theoretician of the 20th century. Early life Theodore von Kármán was born into a Jewish family in Budapest, then part of Austria-Hungary, as Kármán Tódor, the son of Helene (Konn or Kohn, ) and . Among his ancestors were Rabbi Judah Loew ben Bezalel, who was said to be the creator of the Golem of Prague, and Rabbi , who wrote about Zohar. His father, Mór, was a well-known educator, who reformed the Hungarian school system and founded Minta Gymnasium in Budapest. He became an influential figure and became a commissioner of the Ministry of Educa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermann Schlichting
Hermann Schlichting (22 September 1907 – 15 June 1982) was a Germans, German fluid dynamics engineer. Life and work Hermann Schlichting studied from 1926 till 1930 mathematics, physics and applied mechanics at the University of Jena, University of Vienna, Vienne and University of Göttingen, Göttingen. In 1930 he wrote his PhD in Göttingen titled ''Über das ebene Windschattenproblem'' and also in the same year passed the state examination as teacher for higher mathematics and physics. His meeting with Ludwig Prandtl had a long-lasting effect on him. He worked from 1931 till 1935 at the Kaiser Wilhelm Institute for Flow Research in Göttingen. His main research area was fluid flows with viscous effects. Simultaneously he also started working on airfoil aerodynamics. In 1935 Schlichting went to Dornier Flugzeugwerke, Dornier in Friedrichshafen. There he did the planning for the new wind tunnel and after short construction time took charge over it. With it he gained useful ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adolf Busemann
Adolf Busemann (20 April 1901 – 3 November 1986) was a German aerospace engineer and influential Nazi-era pioneer in aerodynamics, specialising in supersonic airflows. He introduced the concept of swept wings and, after emigrating in 1947 to the United States under Operation Paperclip, invented the shockwave-free supersonic Busemann biplane. Education and early life Born in Lübeck, Germany, Busemann attended the Technical University of Braunschweig, receiving his Ph.D. in engineering in 1924. Career and research The next year he was given the position of aeronautical research scientist at the Max-Planck Institute where he joined the famed team led by Ludwig Prandtl, including Theodore von Kármán, Max Munk and Jakob Ackeret. In 1930 he was promoted to professor at University of Göttingen. He held various positions within the German scientific community during this period, and during the war he was the director of the Braunschweig Laboratory, a famous research establishm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Göttingen
The University of Göttingen, officially the Georg August University of Göttingen (, commonly referred to as Georgia Augusta), is a Public university, public research university in the city of Göttingen, Lower Saxony, Germany. Founded in 1734 by George II of Great Britain, George II, King of Great Britain and Electorate of Hanover, Elector of Hanover, it began instruction in 1737 and is recognized as the oldest university in Lower Saxony. Recognized for its historic and traditional significance, the university has affiliations with 47 Nobel Prize winners by its own count. Previously backed by the German Universities Excellence Initiative, the University of Göttingen is a member of the U15 (German Universities), U15 Group of major German research universities, underscoring its strong research profile. It is also a part of prominent international and European academic networks such as Guild of European Research-Intensive Universities, The Guild, the ENLIGHT alliance, and the Hek ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prandtl Condition
In fluid mechanics the Prandtl condition was suggested by the German physicist Ludwig Prandtl to identify possible boundary layer separation points of incompressible fluid In fluid mechanics, or more generally continuum mechanics, incompressible flow is a flow in which the material density does not vary over time. Equivalently, the divergence of an incompressible flow velocity is zero. Under certain conditions, t ... flows. Prandtl condition-in normal shock In the case of normal shock, flow is assumed to be in a steady state and thickness of shock is very small. It is further assumed that there is no friction or heat loss at the shock (because heat transfer is negligible because it occurs on a relatively small surface). It is customary in this field to denote x as the upstream and y as the downstream condition. Since the mass flow rate from the two sides of the shock are constant, the mass balance becomes, \rho_.U_=\rho_.U_ As there is no external force applied, momentum is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Walter Tollmien
Walter Tollmien (13 October 1900, in Berlin Berlin ( ; ) is the Capital of Germany, capital and largest city of Germany, by both area and List of cities in Germany by population, population. With 3.7 million inhabitants, it has the List of cities in the European Union by population withi ... – 25 November 1968, in Göttingen) was a German fluid dynamicist. Life Walter Tollmien studied mathematics and physics for the winter semester in 1920–1921 with Ludwig Prandtl in Göttingen and then from 1924 onwards worked under Prandtl at the Kaiser Wilhelm Institute. After some research in Germany, he went to the United States and stayed there between 1930 and 1933. He became a professor in 1937 at Technische Hochschule Dresden. In 1957, he took over the post of director at the Max-Planck Institute for fluid mechanics research. Achievements Through his pioneering work as a researcher and a teacher, Walter Tollmien brought fluid mechanics into the lime light and as an inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
