BREAKDOWN REGIMES OF INERTIA WAVES IN A PRECESSING CYLINDER

A series of experimental studies have been made of the fluid behaviour in a completely filled, precessing, right circular cylinder. The tank was spun about its axis of symmetry and subjected to a forced precession at various excitation frequencies omega, nutation angles theta and at various Ekman numbers. This forcing excites a subset of the modes, called inertia waves. that are made possible by the Coriolis force that arises in a spinning environment. In these experiments, the fluid flow breakdown phenomena are investigated. Here the fluid, when forced near a resonant frequency, exhibits a transition to disordered or turbulent flow. This paper presents a categorization of some of the breakdown regimes, of which the 'resonant collapses' (McEwan 1970) are the most catastrophic members. The studies reported in this paper used entirely visual observations and measurements. The experimental observations employed a visualization technique that gave no information on fluid velocities, but provided an excellent picture of the flow structure. Quantitative data were extracted in the form of the time for the breakdown to occur. The breakdown phenomena, while readily produced over a large region of parameter space, are complex and varied. The observations show that our system is extraordinarily rich. exhibiting, for example, recurrent breakdowns which may be explained in terms of chaotic intermittency. A detailed description of some of the different breakdown regimes indicates that no single model will explain the behaviour throughout parameter space. This research is motivated by the instability problems of spinning spacecraft containing liquid fuels.