In case you examine indoor heating and cooling system, you probably see that even If heating equipments are available close to ground, cooling equipments are located through ceiling. What is the idea regarding these establishments ? According to ideal gas law, If ideal gas is heated (within constant pressure assumption), density of gas is changed with similar percent. Changes through density results in movement. Therefore, convection that one of the method for heat transfer phenomenon would be realized in a continous loop inside a constant pressurized system (omnipresence of 1 atm in atmosphere). Rayleigh and Bénard discovered this phenomenon which is still studied due to generate an exact model. Rayleigh–Bénard convection is a type of natural convection, occurring in a plane horizontal layer of fluid heated from below, in which the fluid develops a regular pattern of convection cells known as Bénard cells. Rayleigh–Bénard convection is one of the most commonly studied convection phenomena because of its analytical and experimental accessibility.The convection patterns are the most carefully examined example of self-organizing nonlinear systems. Buoyancy, and hence gravity, is responsible for the appearance of convection cells. The initial movement is the upwelling of lesser density fluid from the heated bottom layer. This upwelling spontaneously organizes into a regular pattern of cells. As the Rayleigh number increases, the gravitational forces become more dominant. At a critical Rayleigh number of 1708, instability sets in and convection cells appear. The critical Rayleigh number can be obtained analytically for a number of different boundary conditions by doing a perturbation analysis on the linearized equations in the stable state. On the other hand, Is surface tension important effect on structure of Rayleigh–Bénard convection ? Source: [1] http://www.mis.mpg.de/applan/research/rayleigh.html [2] https://en.wikipedia.org/wiki/Rayleigh%E2%80%93B%C3%A9nard_convection [3] http://web.stanford.edu/~ajlucas/Rayleigh-Benard%20Convection.pdf [4] http://www.nature.com/nature/journal/v404/n6779/full/404733a0.html Here a bonus:
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