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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 ...
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.
This work laid the foundation for the study of Rayleigh–Bénard convection, the buoyancy-driven flow of fluid confined between horizontal conducting surfaces, with the higher temperature at the bottom; and Bénard–Marangoni convection, the surface-tension-driven flow of a fluid with an upper free surface and a heated, conducting surface at ...
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 ...
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 ...
Analyzing the Rayleigh–Bénard convection cell phenomenon, Chandrasekhar (1961) [59] wrote "Instability occurs at the minimum temperature gradient at which a balance can be maintained between the kinetic energy dissipated by viscosity and the internal energy released by the buoyancy force." With a temperature gradient greater than the minimum ...
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 ...