Editing Boussinesq approximation (buoyancy) (section)

{{short description|Simplification for simulating fluids under natural convection}}
{{About|the Boussinesq approximation in buoyancy-driven flows||Boussinesq approximation (disambiguation)}}

In [[fluid dynamics]], the '''Boussinesq approximation''' ({{IPA|fr|businɛsk|pron}}, named for [[Joseph Valentin Boussinesq]]) is used in the field of [[buoyancy]]-driven flow (also known as [[natural convection]]). It ignores [[density]] differences except where they appear in terms multiplied by {{mvar|g}}, the [[Gravitational acceleration|acceleration due to gravity]]. The essence of the Boussinesq approximation is that the difference in [[inertia]] is negligible but gravity is sufficiently strong to make the [[specific weight]] appreciably different between the two fluids. The existence of [[sound|sound waves]] in a Boussinesq fluid is not possible as sound is the result of density fluctuations within a fluid.

Boussinesq flows are common in nature (such as [[surface weather analysis|atmospheric front]]s, oceanic circulation, [[katabatic wind]]s), industry ([[Air pollution dispersion terminology|dense gas dispersion]], fume cupboard ventilation), and the built environment (natural ventilation, [[central heating]]). The approximation can be used to simplify the equations describing such flows, whilst still describing the flow behaviour to a high degree of accuracy.