In
fluid dynamics, the
Boussinesq approximation (, 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
g, the
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.
Sound waves are impossible/neglected when the Boussinesq approximation is used since sound waves move via density variations.