Definition
For free convection near a vertical wall, the Rayleigh number is defined as
where
- x = Characteristic length (in this case, the distance from the leading edge)
- Rax = Rayleigh number at position x
- Grx = Grashof number at position x
- Pr = Prandtl number
- g = acceleration due to gravity
- Ts = Surface temperature (temperature of the wall)
- T∞ = Quiescent temperature (fluid temperature far from the surface of the object)
- ν = Kinematic viscosity
- α = Thermal diffusivity
- β = Thermal expansion coefficient
In the above, the fluid properties Pr, ν, α and β are evaluated at the film temperature, which is defined as
For most engineering purposes, the Rayleigh number is large, somewhere around 106 to 108.
Read more about this topic: Rayleigh Number
Famous quotes containing the word definition:
“According to our social pyramid, all men who feel displaced racially, culturally, and/or because of economic hardships will turn on those whom they feel they can order and humiliate, usually women, children, and animals—just as they have been ordered and humiliated by those privileged few who are in power. However, this definition does not explain why there are privileged men who behave this way toward women.”
—Ana Castillo (b. 1953)
“The physicians say, they are not materialists; but they are:MSpirit is matter reduced to an extreme thinness: O so thin!—But the definition of spiritual should be, that which is its own evidence. What notions do they attach to love! what to religion! One would not willingly pronounce these words in their hearing, and give them the occasion to profane them.”
—Ralph Waldo Emerson (1803–1882)
“Was man made stupid to see his own stupidity?
Is God by definition indifferent, beyond us all?
Is the eternal truth man’s fighting soul
Wherein the Beast ravens in its own avidity?”
—Richard Eberhart (b. 1904)