The slow dripping of a viscous fluid

The problem considered is the determination of the mass of the drops which break away when a viscous liquid drips slowly out of a narrow vertical tube. A simple one-dimensional theory of the unsteady extension of a viscous thread under its own weight is given, which holds when viscosity, capillarity and gravity are important but inertia is negligible. A comparison with experiment is given. There are several systematic errors, the most important of which are associated with detailed behaviour at the pipe exit where die-swell and wetting are difficult to assess. With due allowance for these errors, agreement is fairly good.