We consider the nonlinear spin-up of a rotating stratified fluid in a conical container. An analysis of similarity-type solutions to the relevant boundary-layer problem (Duck, Foster & Hewitt, 1997) has revealed three types of behaviour for this geometry. In general, the boundary-layer evolves to either a steady state, a growing boundary-layer, or a finite-time singularity depending on the initial to final rotation rate ratio, and a “modified Burger number”.
We emphasise the experimental aspects of our continuing spin-up investigations and make some preliminary comparisons with the boundary-layer theory, showing good agreement. The experimental data presented is obtained through particle tracking velocimetry. We briefly discuss the qualitative features of the spin-down experiments which, in general, are dominated by non-axisymmetric effects.
The experiments are performed using a conical container filled with a linearly stratified fluid, the generation of which is non-trivial. We present a general method for creating a linear density profile in containers with sloping boundaries.