Reynolds number

noun

A dimensionless parameter that determines the behavior of viscous flow patterns. In pipe flow a value less than roughly 2,000 (known as the critical Reynolds number) produces laminar flow, one above about 3,000 produces turbulent flow (intermediate values produce unpredictable behavior).

Meanings

nounReynolds number (plural Reynolds numbers)

plural Reynolds numbers

  1. natural sciencesA dimensionless parameter that determines the behavior of viscous flow patterns. In pipe flow a value less than roughly 2,000 (known as the critical Reynolds number) produces laminar flow, one above about 3,000 produces turbulent flow (intermediate values produce unpredictable behavior).

    Reynold Number^([sic]) — It determines the state of flow of liquid through a pipe […]

    1995, Kalra Publications Pvt. Ltd., “Supreme Pocket Master: Physics Formula”, 1st Edition, page 136, verso
    1 more example

    One certainly can argue that not all low-speed streaks lead to liftup, although if the local Reynolds number exceeds the transition limit, it is certain that eventual transition will occur to the hairpin vortex liftup, which ultimately leads to the breakup state.

    1995, William Lawrence Keith, Flow Noise Modeling, Measurement, and Control, page 45

Origin

Named after British engineer Osborne Reynolds.

Full word history & related roots →

Translations

Chinese Mandarin 雷諾數 /雷诺数
  • 雷諾數 /雷诺数 (Léinuòshù)dimensionless parameter of flow
Hungarian Reynolds-féle szám
  • Reynolds-féle számdimensionless parameter of flow
Japanese レイノルズ数
  • レイノルズ数 (Reinoruzu-sū)dimensionless parameter of flow
Polish liczba Reynoldsa
  • liczba Reynoldsadimensionless parameter of flow
Portuguese número de Reynolds
  • número de Reynoldsdimensionless parameter of flow
Russian число́ Рейнольдса
  • число́ Рейнольдса (čisló Rejnolʹdsa)dimensionless parameter of flow
Cite this entry
APA

Reynolds number. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/Reynolds%20number

MLA

“Reynolds number.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/Reynolds%20number. Accessed November 4, 2026.

Chicago

WatkinsX Dictionary, s.v. “Reynolds number,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/Reynolds%20number.

Source: Reynolds number on Wiktionary, CC BY-SA 4.0.