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Buoyancy also applies to fluid mixtures, and is the most common driving force of convection currents. In these cases, the mathematical modelling is altered to apply to continua, but the principles remain the same. Examples of buoyancy driven flows include the spontaneous separation of air and water or oil and water.
This mechanism is found very commonly in everyday life, including central heating and air conditioning and in many other machines. Forced convection is often encountered by engineers designing or analyzing heat exchangers, pipe flow, and flow over a plate at a different temperature than the stream (the case of a shuttle wing during re-entry, for example).
If the buoyancy of an (unrestrained and unpowered) object exceeds its weight, it tends to rise. An object whose weight exceeds its buoyancy tends to sink. Calculation of the upwards force on a submerged object during its accelerating period cannot be done by the Archimedes principle alone; it is necessary to consider dynamics of an object ...
Profiling buoys are specialized buoys that adjust their buoyancy to sink at a controlled rate to a set depth, for example 2,000 metres while measuring sea temperature and salinity. After a certain period, typically 10 days, they return to the surface, transmit their data via satellite, then sink again. [ 18 ]
Buoyancy is important in many fields. Boats, ships and seaplanes are engineered in a way that ensures that they remain afloat. Submarines have controllable buoyancy to make them submerge and rise on demand. Many objects were developed with buoyancy in mind, such as life preservers and pontoons. Buoyancy is essential to most water sports.
Hydrostatics offers physical explanations for many phenomena of everyday life, such as why atmospheric pressure changes with altitude, why wood and oil float on water, and why the surface of still water is always level according to the curvature of the earth.
"Buoyancy is defined as being positive" when, in the absence of other forces or initial motion, the entering fluid would tend to rise. Situations where the density of the plume fluid is greater than its surroundings (i.e. in still conditions, its natural tendency would be to sink), but the flow has sufficient initial momentum to carry it some ...
Gases at high pressure can have a density exceeding that of some solids. Thus they can be used to levitate solid objects through buoyancy. [5] Noble gases are preferred for their non-reactivity. Xenon is the densest non-radioactive noble gas, at 5.894g/L. Xenon has been used to levitate polyethylene, at a pressure of 154atm.