page_title: Stable and unstable stratification
section_title: Engineering
hierarchical_section_title: Stable and unstable stratification / Applications / Engineering
caption_attribution_description: English: Air stratification capitalizes on thermal buoyancy to layer high quality supply air at occupant level and leave unoccupied air unconditioned.
context_page_description: Stable stratification of fluids occurs when each layer is less dense than the one below it. Unstable stratification is when each layer is more dense than the one below it.
  Buoyancy forces tend to preserve stable stratification; the higher layers float on the lower ones. In unstable stratification, on the other hand, buoyancy forces cause convection. The less-dense layers rise though the more-dense layers above, and the more-dense layers sink though the less-dense layers below. Stratifications can become more or less stable if layers change density. The processes involved are important in many science and engineering fields.
context_section_description: In engineering applications, stable stratification or convection may or may not be desirable. In either case it may be deliberately manipulated. 
  Stratification can strongly affect the mixing of fluids, which is important in many manufacturing processes.
  Underfloor heating deliberately creates unstable stratification of the air in a room.
  Passive cooling relies on selectively encouraging and disrupting stable stratification to cool rooms.
caption: Vertical temperature gradient cause by stable stratification of air inside a room. Note hot air rising convectively from the person; bodyheat temporarily disrupts the stable stratification.
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