An anelastic approximation is a filtering approximation for the equations of motion that eliminates sound waves by assuming that the flow has velocities and phase speeds much smaller than the speed of sound. Applications of the anelastic approximation occur most commonly in meteorology, atmospheric science and ocean studies. In its purest form, it requires that the reference state be isentropic as well as hydrostatic, although in practice the reference state is often taken to be nonisentropic which can have deleterious effects on the energy conservation properties of the full set of equations. The anelastic approximation is one of the set of approximations used for the somewhat similar Boussinesq approximation.
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- Boussinesq approximation
- Physical Oceanography Index
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- Seas of the World on the Encyclopedia of Earth