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Laminar–turbulent Transition
In fluid dynamics, the process of a Laminar flow, laminar flow becoming turbulent is known as laminar–turbulent transition. The main parameter characterizing transition is the Reynolds number. Transition is often described as a process proceeding through a series of stages. ''Transitional flow'' can refer to transition in either direction, that is laminar–turbulent transitional or turbulent–laminar transitional flow. The process applies to any fluid flow, and is most often used in the context of boundary layers. History In 1883 Osborne Reynolds demonstrated the transition to turbulent flow in a classic experiment in which he examined the behaviour of water flow under different flow rates using a small jet of dyed water introduced into the centre of flow in a larger pipe. The larger pipe was glass, so the behaviour of the layer of dyed flow could be observed, and at the end of this pipe was a flow-control valve used to vary the water velocity inside the tube. When the ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Hydrodynamic Stability
In fluid dynamics, hydrodynamic stability is the field of study, field which analyses the stability and the onset of instability of fluid flows. The study of hydrodynamic stability aims to find out if a given flow is stable or unstable, and if so, how these instabilities will cause the development of turbulence.See Drazin (2002), ''Introduction to hydrodynamic stability'' The foundations of hydrodynamic stability, both theoretical and experimental, were laid most notably by Hermann von Helmholtz, Helmholtz, William Thomson, 1st Baron Kelvin, Kelvin, John Strutt, 3rd Baron Rayleigh, Rayleigh and Osborne Reynolds, Reynolds during the nineteenth century. These foundations have given many useful tools to study hydrodynamic stability. These include Reynolds number, the Euler equations (fluid dynamics), Euler equations, and the Navier–Stokes equations. When studying flow stability it is useful to understand more simplistic systems, e.g. incompressible and inviscid fluids which can then ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between those layers. Turbulence is commonly observed in everyday phenomena such as surf, fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent. Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason, turbulence is commonly realized in low viscosity fluids. In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. The onset of turbulence can be predicted by the dimensionless Reynolds number, the ratio of kinetic energy to viscous damping ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Chaos Theory
Chaos theory is an interdisciplinary area of Scientific method, scientific study and branch of mathematics. It focuses on underlying patterns and Deterministic system, deterministic Scientific law, laws of dynamical systems that are highly sensitive to initial conditions. These were once thought to have completely random states of disorder and irregularities. Chaos theory states that within the apparent randomness of chaotic complex systems, there are underlying patterns, interconnection, constant feedback loops, repetition, self-similarity, fractals and self-organization. The butterfly effect, an underlying principle of chaos, describes how a small change in one state of a deterministic nonlinear system can result in large differences in a later state (meaning there is sensitive dependence on initial conditions). A metaphor for this behavior is that a butterfly flapping its wings in Brazil can cause or prevent a tornado in Texas. Text was copied from this source, which is avai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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] [Amazon] |
Boundary Layers
In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a 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 viscous forces distort the surrounding non-viscous flow. In the Earth's atmosphere, the atmospheric boundary la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Transition Modeling
Transition modeling is the use of a model to predict the change from laminar and turbulent flows in fluids and their respective effects on the overall solution. The complexity and lack of understanding of the underlining physics of the problems makes simulating the interaction between laminar and turbulent flow to be difficult and very case specific. Transition does have the wide range of turbulence options available for most computational fluid dynamics (CFD) applications for the following reasons: * Transition involves a wide range of scales where the energy and momentum transfer are strongly influenced by inertial or non-linear effects that are unique to the simulation. * Transition also occurs by different means, such as natural and bypass, and modeling all possibilities is difficult. Most CFD programs use Reynolds-averaged Navier–Stokes equations, in which averaging eliminates linear disturbance. Common models The following is a list of commonly employed transition models ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Lord Rayleigh
John William Strutt, 3rd Baron Rayleigh ( ; 12 November 1842 – 30 June 1919), was an English physicist who received the Nobel Prize in Physics in 1904 "for his investigations of the densities of the most important gases and for his discovery of argon in connection with these studies". He served as president of the Royal Society from 1905 to 1908 and as chancellor of the University of Cambridge from 1908 to 1919. Rayleigh provided the first theoretical treatment of the elastic scattering of light by particles much smaller than the light's wavelength, a phenomenon now known as "Rayleigh scattering", which notably explains why the sky is blue. He studied and described transverse surface waves in solids, now known as "Rayleigh waves". He contributed extensively to fluid dynamics, with concepts such as the Rayleigh number (a dimensionless number associated with natural convection), Rayleigh flow, the Rayleigh–Taylor instability, and Rayleigh's criterion for the stability of Ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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] [Amazon] |
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] [Amazon] |
Aurora Leigh
''Aurora Leigh'' is an 1856 verse novel by Elizabeth Barrett Browning. The poem is written in blank verse and encompasses nine books (the woman's number, the number of the Sibylline Books). It is a first-person narration, from the point of view of Aurora; its other heroine, Marian Erle, is an abused self-taught child of itinerant parents. The poem is set in Florence, Malvern, London and Paris. The work references Biblical and classical history and mythology, as well as modern novels, such as '' Corinne ou l'Italie'' by Anne Louise Germaine de Staël and the novels of George Sand. In Books 1–5, Aurora narrates her past, from her childhood to the age of about 27; in Books 6–9, the narrative has caught up with her, and she reports events in diary form. The author styled the poem "a novel in verse", and referred to it as "the most mature of my works, and the one into which my highest convictions upon Life and Art have entered". The scholar Deirdre David asserts that Barrett Br ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
