Physics & Chemistry

# Buoyancy frequency

October 28, 2011, 4:35 pm
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 This article is written at a definitional level only. Authors wishing to improve this entry are inivited to expand the present treatment, which additions will be peer reviewed prior to publication of any expansion.

Buoyancy frequency is the frequency with which a parcel or particle of fluid displaced a small vertical distance from its equilibrium position in a stable environment will oscillate. This concept, also termed the Brunt–Väisälä frequency, can apply to a liquid or gaseous medium. The parcel will oscillate in simple harmonic motion with an angular frequency defined by:

where g is the gravitational acceleration, θ is the potential temperature, α is the thermal expansion coefficient, and β is the saline contraction coefficient. In practice, the equivalent formula:

is often used, where c is the velocity of sound, although care must be taken to consistently evaluate ρ and c.