Reynolds number

Reynolds number
n.
〚after O. Reynolds (1842-1912), Eng physicist〛
a dimensionless parameter used to determine the nature of fluid flow along surfaces and around objects, as in a wind tunnel

* * *

In fluid mechanics, a number that indicates whether the flow of a fluid (liquid or gas) is absolutely steady (in streamlined, or laminar flow) or on the average steady with small, unsteady changes (in turbulent flow; see turbulence).

The Reynolds number, abbreviated NRe or Re, has no dimensions (see dimensional analysis) and is defined as the size of the flow
as, for example, the diameter of a tube (D) times the average speed of flow (v) times the mass density of the fluid (ρ)
divided by its absolute viscosity (μ). Osborne Reynolds demonstrated in 1883 that the change from laminar to turbulent flow in a pipe occurs when the value of the Reynolds number exceeds 2,100.

* * *

      in fluid mechanics, a criterion of whether fluid (liquid or gas) flow is absolutely steady (streamlined, or laminar (laminar flow)) or on the average steady with small unsteady fluctuations (turbulent). Whenever the Reynolds number is less than about 2,000, flow in a pipe is generally laminar, whereas, at values greater than 2,000, flow is usually turbulent. Actually, the transition between laminar and turbulent flow occurs not at a specific value of the Reynolds number but in a range usually beginning between 1,000 to 2,000 and extending upward to between 3,000 and 5,000.

      In 1883 Osborne Reynolds (Reynolds, Osborne), a British engineer and physicist, demonstrated that the transition from laminar to turbulent flow in a pipe depends upon the value of a mathematical quantity equal to the average velocity of flow times the diameter of the tube times the mass density of the fluid divided by its absolute viscosity. This mathematical quantity, a pure number without dimensions, became known as the Reynolds number and was subsequently applied to other types of flow that are completely enclosed or that involve a moving object completely immersed in a fluid.

* * *


Universalium. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Reynolds number — n. [after O. Reynolds (1842 1912), Eng physicist] a dimensionless parameter used to determine the nature of fluid flow along surfaces and around objects, as in a wind tunnel …   English World dictionary

  • Reynolds number — In fluid mechanics and heat transfer, the Reynolds number mathrm{Re} is a dimensionless number that gives a measure of the ratio of inertial forces ({old mathrm V} ho) to viscous forces (mu / L) and, consequently, it quantifies the relative… …   Wikipedia

  • Reynolds number — A dimensionless number that establishes the proportionality between the fluid inertia and the sheer stress as a result of viscosity. The work of Osborne Reynolds has shown that the flow profile of fluid in a closed circuit depends upon the… …   Aviation dictionary

  • reynolds number — n. Physics a quantity indicating the degree of turbulence of flow past an obstacle etc. Etymology: O. Reynolds, Engl. physicist d. 1912 * * * ˈrenəldz noun Usage: usually capitalized R Etymology: after Osborne Reynolds died 1912 English physicist …   Useful english dictionary

  • Reynolds number — /ˈrɛnəldz nʌmbə/ (say renuhldz numbuh) noun a dimensionless number which determines whether the fluid flow in a particular situation will be streamline or turbulent. It is important in hydrodynamics and aeronautics since models with the same… …  

  • Reynolds number — Reinoldso skaičius statusas T sritis fizika atitikmenys: angl. Reynolds number vok. Reynolds Zahl, f rus. число Рейнольдса, n pranc. nombre de Reynolds, m …   Fizikos terminų žodynas

  • Reynolds number — Reinoldso skaičius statusas T sritis Energetika apibrėžtis Apibrėžtį žr. priede. priedas( ai) MS Word formatas atitikmenys: angl. Reynolds number vok. Reynolds Zahl, f rus. Рейнольдса число, n pranc. nombre de Reynolds, m …   Aiškinamasis šiluminės ir branduolinės technikos terminų žodynas

  • Reynolds number — Reinoldso skaičius statusas T sritis Standartizacija ir metrologija apibrėžtis Apibrėžtį žr. priede. priedas( ai) Grafinis formatas atitikmenys: angl. Reynolds number vok. Reynoldssche Zahl, f; Reynoldszahl, f rus. число Рейнольдса, n pranc.… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • Reynolds number — noun a dimensionless parameter that determines the behavior of viscous flow patterns. In pipe flow a value less than about 2,000 (known as the critical Reynolds number) produces laminar flow, one above about 3,000 produces turbulent flow… …   Wiktionary

  • Reynolds number — Reinoldso skaičius statusas T sritis chemija apibrėžtis Skysčio arba dujų inercijos ir klampos jėgų santykis. atitikmenys: angl. Reynolds number rus. критерий Рейнольдса; число Рейнольдса ryšiai: sinonimas – Reinoldso kriterijus …   Chemijos terminų aiškinamasis žodynas

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”