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IEVref: | 113-04-58 | ID: | |

Language: | en | Status: Standard | |

Term: | Rayleigh number | ||

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Symbol: | Ra
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Definition: | quantity of dimension 1 characterizing the relative importance of natural convection and thermal conduction, defined by $Ra=\frac{{l}^{3}{\rho}^{2}{c}_{p}\text{\hspace{0.05em}}g\text{\hspace{0.05em}}{\alpha}_{V}\text{\hspace{0.05em}}\Delta T}{\eta \text{\hspace{0.05em}}\lambda}=\frac{{l}^{3}g\text{\hspace{0.05em}}{\alpha}_{V}\text{\hspace{0.05em}}\Delta T}{\nu \text{\hspace{0.05em}}\alpha}$, where l is a specified length, ρ is mass density, c_{p} is specific heat capacity at constant pressure, g is acceleration of free fall, α_{v} is the cubic expansion coefficient, T is thermodynamic temperature, η is dynamic viscosity, λ is thermal conductivity, and α is thermal diffusivityNOTE The Rayleigh number is the product of the Grashof number | ||

Publication date: | 2011-04 | ||

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Internal notes: | 2015-11-02: Note corrected from "NOTE The Rayleigh number is the product of the Grashof number <i>Re</i>" to "NOTE The Rayleigh number is the product of the Grashof number <i>Gr</i>" in accordance with mail from Reinhard Salffner. JGO 2017-06-02: Cleanup - Remove Attached Image 113-04-58en.gif | ||

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NOTE The Rayleigh number is the product of the Grashof number *Gr* and the Prandtl number *Pr*, thus *Ra* = *Gr* ⋅ *Pr*.