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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 ...
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]
In fluid dynamics, convective mixing is the vertical transport of a fluid and its properties. In many important ocean and atmospheric phenomena, convection is driven by density differences in the fluid, e.g. the sinking of cold, dense water in polar regions of the world's oceans; and the rising of warm, less-dense air during the formation of cumulonimbus clouds and hurricanes.
Thermal image of a newly lit Ghillie kettle. The plume of hot air resulting from the convection current is visible. Convective flow may be transient (such as when a multiphase mixture of oil and water separates) or steady state (see convection cell). The convection may be due to gravitational, electromagnetic or fictitious body forces.
In many real-life applications (e.g. heat losses at solar central receivers or cooling of photovoltaic panels), natural and forced convection occur at the same time (mixed convection). [4] Internal and external flow can also classify convection. Internal flow occurs when a fluid is enclosed by a solid boundary such as when flowing through a pipe.
The polar cell is a simple system with strong convection drivers. Though cool and dry relative to equatorial air, the air masses at the 60th parallel are still sufficiently warm and moist to undergo convection and drive a thermal loop. At the 60th parallel, the air rises to the tropopause (about 8 km at this latitude) and moves poleward.
A diagram of the internal structure of Earth. The lithosphere consists of the crust and upper solid mantle (lithospheric mantle). The green dashed line marks the LAB. The lithosphere–asthenosphere boundary (referred to as the LAB by geophysicists) represents a mechanical difference between layers in Earth's inner structure.
Basic diagram of a focusing schlieren system. The basic idea is that the illumination pattern is imaged onto a geometrically congruent cutoff pattern (essentially a multiplicity of knife edges) with focusing optics, while density gradients lying between the illumination pattern and the cutoff pattern are imaged, typically by a camera system.