Dynamics of a Pipe Aspirating Fluid Such as Might be Used in Ocean Mining

This paper presents an investigation into the dynamics and stability of a long, vertically disposed, cantilevered pipe, submerged in and aspirating fluid from the free lower end, and conveying it upwards to the supported upper end; the pipe has a large mass attached to its free end. The arrangement represents an idealization of an ocean mining system. This paper reports on the first phase of this work, in which the following simplifications have been made: (i) the pipe is straight at equilibrium; (ii) the effects of marine currents and wave action are not considered. It is shown that under the action of the internal flow, the system is inherently unstable, by flutter, and that it does not lose stability at vanishingly small flow velocities, only because of dissipation, through friction with the external fluid medium. Effective passive stabilization of the system may be achieved through artificial augmentation of this form of dissipation.