Rayleigh Number

Written by Jerry Ratzlaff. Posted in Dimensionless Numbers

Rayleigh Number is a dimensionless number and a modified Grashof Number used for natural convection calculations.

FORMULA

\(Ra=\frac{\rho g  \alpha_c  \Delta T L^3}{\mu  \alpha}\)

Where:

\(Ra\) = Rayleigh Number

\(\rho\) (Greek symbol rho) = fluid density

\(g\) = gravitational acceleration

\(\alpha_c\) (Greek symbol alpha) = thermal expansion coefficient

\(\Delta T\) = temperature differential

\(l\) = length

\(\mu\) (Greek symbol mu) = absolute viscosity

\(\alpha\) (Greek symbol alpha) = thermal diffusivity