Astronomy: General

A Dictionary of Astronomy A Dictionary of Earth Sciences Further reading

Rayleigh number

A Dictionary of Astronomy | 1997 | Copyright

Rayleigh number (symbol Ra) A parameter that determines when convection may occur in a gas or liquid. Convection can occur when more energy is gained by moving material than is lost to friction. The Rayleigh number is dimensionless and depends on the local gravitational acceleration and the properties of the material. Convection occurs when the Rayleigh number exceeds a critical limit. The Rayleigh number is used in modelling stellar and planetary interiors and planetary atmospheres. It is named after Lord Rayleigh.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"Rayleigh number." A Dictionary of Astronomy. 1997. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>.

"Rayleigh number." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O80-Rayleighnumber.html

"Rayleigh number." A Dictionary of Astronomy. 1997. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-Rayleighnumber.html

Learn more about citation styles

Rayleigh number

A Dictionary of Earth Sciences | 1999 | | Copyright

Rayleigh number (Ra) A dimensionless value used to estimate when convection commences in a fluid. The Ra depends on the density and depth of the fluid, the coefficient of thermal expansion, the gravitational field, the temperature gradient (in excess of the adiabatic 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.

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

AILSA ALLABY and MICHAEL ALLABY. "Rayleigh number." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>.

AILSA ALLABY and MICHAEL ALLABY. "Rayleigh number." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O13-Rayleighnumber.html

AILSA ALLABY and MICHAEL ALLABY. "Rayleigh number." A Dictionary of Earth Sciences. 1999. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-Rayleighnumber.html

Learn more about citation styles

Free newspaper and magazine articles

	Dynamic two-phase truncated Rayleigh model for release date prediction of... Magazine article from: Journal of Software Engineering and Applications (JSEA); 6/1/2010
	QPSK DS-CDMA system over Rayleigh channel with a randomly-varying frequency... Magazine article from: Wireless Sensor Network (WSN); 3/1/2010
	Algebraic number theory and code design for Rayleigh fading channels. Magazine article from: Foundations and Trends in Communications and Information Theory; 12/1/2004