Dynamics of spinning pipes conveying fluid
Think of the wild, snaking motion of a garden hose when you drop it on the ground, or the kick you feel in your hand when you open the tap too far. These are instabilities caused by flow. Add rotation to the picture and the behaviour becomes far more complicated, and that is what this thesis is about.
A spinning pipe carrying fluid is not an exotic object. An oil drill string turns while drilling fluid is pumped through it, and the same combination appears wherever slender tubes rotate and carry a flow. Each effect alone can shake such a pipe into violent motion, and together they interact, so neither can be understood in isolation.
This thesis develops a general mathematical model that predicts precisely how such a system behaves across a wide range of rotation speeds and flow rates: when it stays stable, when it loses stability, and the kind of motion it settles into afterwards. The model applies broadly, from kilometre-long marine risers and deep-sea mining pipes drawing oil and minerals up from the seabed, all the way down to micro-scale resonators.