Nonlinear spin-up of a rotating stratified fluid: Experimental method and preliminary results

We consider the nonlinear spin-up of a rotating stratified fluid in a conic al container Art analysis of similarity-type solutions to the relevant boun dary-layer problem (Duck et al., 1997) has revealed three types of behavior for this geometry. In general, the boundary-layer evolves to either a stea dy state, a growing boundary-layer, or a finite-time singularity depending art the initial to final rotation rate ratio, and a "modified Burger number ." We emphasize the experimental aspects of our continuing spin-up investig ations and make some preliminary comparisons with the boundary-layer theory , showing good agreement. The experimental data presented is obtained throu gh particle tracking velocimetry. We briefly discuss the qualitative featur es of the the spin down experiments which, in general, are dominated by non axisymmetric effects. The experiments are performed using a conical contain er filled with a linearly stratified fluid, the generation of which is nont rivial. We present a general method for creating a linear density profile i n containers with sloping boundaries.