Definition 19.2University Earth and Space Sciences — Year 3 · 第 19 章 — Geophysical Fluid Dynamics
The Boussinesq approximation writes the density as ρ=ρ0+ρ′, with ρ0 a constant and ∣ρ′∣≪ρ0, and keeps ρ′ only where it is multiplied by g. The continuity equation becomes ∇⋅u=0, and the momentum equation
DtDu+fk×u=−ρ01∇p′+bk+ν∇2u,b=−gρ0ρ′,
where p′ is the departure of the pressure from the hydrostatic pressure of the density ρ0, k the upward unit vector and b the buoyancy.