Rayleigh number (Ra) — An Etymological Dictionary of Astronomy and Astrophysics

Rayleigh number (Ra)

عدد ِ ریلی

adad-e Rayleigh

Fr.: nombre de Rayleigh

The ratio of the buoyancy force to the viscous force in a medium. This dimensionless number is used to estimate when convection commences in a fluid. It depends on the density and depth of the
fluid, the coefficient of thermal expansion, the gravitational field,
the temperature gradient, the thermal diffusivity, and the kinematic viscosity. Convection usually starts when Ra is 1000 or more, while heat transfer is entirely by conduction when Ra is less than 10.

See also: → rayleigh; → number.

An Etymological Dictionary of Astronomy and Astrophysics

English-French-Persian

فرهنگ ریشه‌شناختی اخترشناسی-اخترفیزیک