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Buoyancy, and hence gravity, are responsible for the appearance of convection cells. The initial movement is the upwelling of less-dense fluid from the warmer bottom layer. [8] This upwelling spontaneously organizes into a regular pattern of cells. Rayleigh–Bénard convection produces complex patterns of frost damage in grass. [9]
Convection is caused by yeast releasing CO2. In fluid dynamics, a convection cell is the phenomenon that occurs when density differences exist within a body of liquid or gas. These density differences result in rising and/or falling convection currents, which are the key characteristics of a convection cell. When a volume of fluid is heated, it ...
Another instance of the Marangoni effect appears in the behavior of convection cells, the so-called Bénard cells. One important application of the Marangoni effect is the use for drying silicon wafers after a wet processing step during the manufacture of integrated circuits. Liquid spots left on the wafer surface can cause oxidation that ...
He also measured the aspect ratio of the cells and discovered that there was a critical temperature below which no convection occurs. Unfortunately, he attributed this to the solidification of the fluid he was using (spermaceti, a whale oil that is solid at room temperature). Ironically, Bénard would much later become a skeptic about the very ...
A fluid under Rayleigh–Bénard convection: the left picture represents the thermal field and the right picture its two-dimensional Fourier transform. Convection, especially Rayleigh–Bénard convection, where the convecting fluid is contained by two rigid horizontal plates, is a convenient example of a pattern-forming system.
The choice R(u) = u(1 − u) yields Fisher's equation that was originally used to describe the spreading of biological populations, [3] the Newell–Whitehead-Segel equation with R(u) = u(1 − u 2) to describe Rayleigh–Bénard convection, [4] [5] the more general Zeldovich–Frank-Kamenetskii equation with R(u) = u(1 − u)e-β(1-u) and 0 ...
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In fluid mechanics, the Rayleigh number (Ra, after Lord Rayleigh [1]) for a fluid is a dimensionless number associated with buoyancy-driven flow, also known as free (or natural) convection. [ 2 ] [ 3 ] [ 4 ] It characterises the fluid's flow regime: [ 5 ] a value in a certain lower range denotes laminar flow ; a value in a higher range ...