Coalescence (meteorology)

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Coalescence is the process by which two or more droplets or particles merge during contact to form a single daughter droplet (or bubble). It can take place in many processes, ranging from meteorology to astrophysics. For example, it is both involved in the formation of raindrops as well as planetary and star formation.

In meteorology, its role is crucial in the formation of rain. As droplets are carried by the updrafts and downdrafts in a cloud, they collide and coalesce to form larger droplets. When the droplets become too large to be sustained on the air currents, they begin to fall as rain. Adding to this process, the cloud may be seeded with ice from higher altitudes either by the cloud tops reaching −40 degrees Celsius or the cloud being seeded by ice from cirrus clouds.

Coalescence is also a term used in welding. Two (or possibly more) pieces of metal are bonded together by liquifying the places where they are to be bonded, coalescing these liquids, and allowing the coalesced liquid to solidify. At the end of this process the two pieces of metal have become one continuous solid, and if the weld has been made properly, it will be as strong as the original workpieces.

[edit] See also

• Bergeron process
• Coalescer

[edit] External links

• Schlumberger Oilfield Glossary
• The Bergeron Process
• The Coalescence of Bubbles - A Numerical Study

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