Vibrations of Long Marine Pipes due to Vortex Shedding

Abstract

Lateral vibrational displacements and accelerations due to vortex shedding are analyzed for very long marine pipes with a bottom end mass for application to deep ocean-mining lift pipes. Estimates of maximum RMS values of displacement and acceleration are presented for a range of tow speeds, pipe lengths, pipe diameters and wall thicknesses, and for various values of the pipe end mass. In contrast to the case of short pipes, higher modes of pipe vibration can be excited even at low towing speeds. In addition, the critical tow speeds, at which the vortex-shedding frequency equals a pipe natural frequency, are closely spaced, and there are no speeds where the vibrations vanish.