REYNOLDS NUMBER

Domain	Definition
Aerospace	(After Osborne Reynolds (1842-1912), English scientist.) A nondimensional parameter representing the ratio of the momentum forces to the viscous forces in fluid flow. In aerodynamics, the Reynolds number of fluid flow about a body is often expressed as the fraction ? = Vl/� where ? is the density of the fluid, V is its velocity, l is a characteristic dimension of the body, and � is the coefficient of viscosity of the fluid. See critical Reynolds number, effective Reynolds number. As applied to the flow of gas through a circular tube the Reynolds number is a dimensionless quantity equal to the product of the gas density, ? , in grams per cubic centimeter; times the flow velocity v, in centimeters per second; times the tube diameter, d, in centimeters; divided by the viscosity coefficient �, in poises:R = ? vd/�Symbol R, NRe. (references)
Meteorology & Standards	The ratio of inertial and viscous forces in a fluid defined by the formula Re = rVD/(mu), where r = density of fluid, (mu)= viscosity in centipoise(CP), V = velocity, and D = inside diameter of pipe. Source: European Union. (references)
Mining	A numerical quantity used as an index to characterize the type of flow in a hydraulic structure in which resistance to motion depends on the viscosity of the liquid in conjunction with the resisting force of inertia. It is the ratio of inertia forces to viscous forces, and is equal to the product of a characteristic velocity of the system (e.g., the mean, surface, or maximum velocity) and a characteristic linear dimension, such as diameter or depth, divided by the kinematic viscosity of the liquid; all expressed in consistent units in order that the combinations will be dimensionless. The number is chiefly applicable to closed systems of flow, such as pipes or conduits where there is free water surface, or to bodies fully immersed in the fluid so the free surface need not be considered. (references)
Nuclear Energy & Physics	A dimensionless number, defined by the identity Re = rho w sub0 1 sub 0:mu where rho and mu are the density and the coefficient of fluid viscosity; w sub 0 is the characteristic velocity of the fluid;1 sub 0 is the characteristic dimension. Source: European Union. (references)
Source: compiled by the editor from various references; see credits.

Specialty Definition: Reynolds number

The Reynolds number is the most important dimensionless number in fluid dynamics providing a criterion for dynamic similarity. It is named after Osbourne Reynolds (1842-1912). Typically it is given as follows:

With:

v_s - mean fluid velocity,
L - characteristic length (equal to diameter 2r if a cross-section is circular),
η - (absolute) dynamic fluid viscosity,
ν - kinematic fluid viscosity: ν = η / ρ,
ρ - fluid density.

The Reynolds number is used for determing whether a flow is laminar or turbulent. Laminar flow within e.g. pipes will occur when the Reynolds number is below the critical Reynolds number of Re_{crit, pipe} = 2300 (or practically Re > 3000) and turbulent flow when it is above 2300 where the Reynolds number is based on the pipe diameter and the mean velocity v_s within the pipe. The value of 2300 has been determined experimentally and a certain range around this value is considered the transition region between laminar and turbulent flow. Please note, that the critical Reynolds number Re_crit depends on the flow type and the definition of the Reynolds number.

The similarity of flows

Two flows with equal Reynolds numbers and the same geometry are similar. For the flow in a model and the real flow holds in appropriate points:

Quantities marked with * concern the flow around the model and the others the real flow. This is useful for experiments with reduced model in the water channel or in the wind tunnel, where we get data for the real flows. Note that in compressible flow the Mach number must also be equal for the two flows to be similar.

See also: Hagen-Poiseuille law, Darcy-Weisbach equation.

Expressions: REYNOLDS NUMBER

Modern Translation: REYNOLDS NUMBER

Language		Translations for "REYNOLDS NUMBER"; alternative meanings/domain in parentheses.
Danish		reynolds tal. (various references)

Dutch		Reynoldsgetal, Re (Ra, Re), kengrootheid van Reynolds, getal van Reynolds. (various references)

Finnish		virtauksen Reynolds-luku. (various references)

French		nombre de Reynolds (pipe Reynolds number). (various references)

German		Re-Zahl (Re, Reynolds parameter, R'group), Reynolds-Zahl (Re, Reynolds parameter, R'group), Reynoldische Zahl, Re-Wert (Re, Reynolds parameter, R'group), Re (re), Damkoehlerzahl (Re, Reynolds parameter, R'group). (various references)

Greek		αριθμός Reynolds. (various references)

Hungarian		reynolds-szám. (various references)

Italian		Numero di Reynolds (Re, Reynolds parameter, R'group). (various references)

Pig Latin		eynoldsray umbernay

Portuguese		parâmetro de Reynolds (Re, Reynolds parameter, R'group), número de Reynolds (Re, Reynolds parameter, R'group), grupo R (Re, Reynolds parameter, R'group). (various references)

Spanish		número Reynolds (Re, Reynolds parameter, R'group), número de Reynolds, índice de Reynolds. (various references)

Swedish		reynoldstal. (various references)
Source: compiled by the editor from various translation references.

Anagrams: REYNOLDS NUMBER

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "b-d-e-e-l-m-n-n-o-r-r-s-u-y"
	-4 letters: blunderers, burdensome, nurserymen, rebounders.
	-5 letters: bemusedly, blunderer, burdeners, emboldens, emborders, ennoblers, lumberers, numberers, rebeldoms, rebounder, redoubles, renumbers, roundsmen, slumbered, slumberer.
Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro.

Alternative Orthography: REYNOLDS NUMBER

Hexadecimal (or equivalents, 770AD-1900s) (references)

52 45 59 4E 4F 4C 44 53 4E 55 4D 42 45 52

Leonardo da Vinci (1452-1519; backwards) (references)

Binary Code (1918-1938, probably earlier) (references)

01010010 01000101 01011001 01001110 01001111 01001100 01000100 01010011 00100000 01001110 01010101 01001101 01000010 01000101 01010010

HTML Code (1990) (references)

&#82 &#69 &#89 &#78 &#79 &#76 &#68 &#83 &#32 &#78 &#85 &#77 &#66 &#69 &#82

ISO 10646 (1991-1993) (references)

0052 0045 0059 004E 004F 004C 0044 0053 004E 0055 004D 0042 0045 0052

Encryption (beginner's substitution cypher): (references)

REYNOLDS NUMBER

Specialty Definition: REYNOLDS NUMBER

Aerospace

Meteorology & Standards

Mining

Nuclear Energy & Physics

Specialty Definition: Reynolds number

The similarity of flows

Crosswords: REYNOLDS NUMBER

Expressions: REYNOLDS NUMBER

Modern Translation: REYNOLDS NUMBER

Danish

Dutch

Finnish

French

German

Greek

Hungarian

Italian

Pig Latin

Portuguese

Spanish

Swedish

Anagrams: REYNOLDS NUMBER

Scrabble® Enable2K-Verified Anagrams

Alternative Orthography: REYNOLDS NUMBER

52 45 59 4E 4F 4C 44 53 4E 55 4D 42 45 52

01010010 01000101 01011001 01001110 01001111 01001100 01000100 01010011 00100000 01001110 01010101 01001101 01000010 01000101 01010010

&#82 &#69 &#89 &#78 &#79 &#76 &#68 &#83 &#32 &#78 &#85 &#77 &#66 &#69 &#82

0052 0045 0059 004E 004F 004C 0044 0053 004E 0055 004D 0042 0045 0052

52395948494638532485547363952

INDEX

Expressions using "REYNOLDS NUMBER": critical Reynolds number ♦ effective Reynolds number. Additional references.
Source: compiled by the editor from various references; see credits.