Rayleigh Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Rayleigh Number

Rayleigh number ( \(Ra\) ) (dimensionless number) and a modified Grashof number used for natural convection calculations.

Rayleigh Number FORMULA

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

Where:

\(\large{ Ra }\) = Rayleigh number

\(\large{ \rho }\)  (Greek symbol rho) = fluid density

\(\large{ g }\) = gravitational acceleration

\(\large{ \alpha_c }\)  (Greek symbol alpha) = thermal expansion coefficient

\(\large{ \Delta T }\) = temperature differential

\(\large{ l }\) = length

\(\large{ \mu }\)  (Greek symbol mu) = absolute viscosity

\(\large{ \alpha }\)  (Greek symbol alpha) = thermal diffusivity

 

Tags: Equations for Force