 Radially symmetric incompressible flow in a planar annulus

ID: radially-symmetric-incompressible-flow-in-a-planar-annulus

Codex  0 Created 2026-09-24 Updated 2026-09-24

For liquid occupying

a (t) < r < b (t)

u_{r} (r, t) = \frac{a a ˙}{r}, ϕ (r, t) = a \overset{a}{˙} lo g r + C (t) .

The kinematic boundary condition at the outer interface gives

b^{2} - a^{2} = constant,

which expresses conservation of the liquid's area.

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