The dynamic behaviour of a surface hose attached to a calm buoy

Abstract

The objective of this study is a quantitative understanding of the mechanisms by which bending moments and axial loads are induced on a floating hose-string attached to a CALM buoy by the combined action of waves and buoy motions. The study is based on physical model tests in which the CALM buoy wi th floating hose-string attached is modelled in a wave basin facility. Simul taneous measurements are recorded of the waves, buoy motions and bending moments or axial loads along the hose-string. orthogonal planes is considered: vertical bending Bending in two in the plane perpendicular to the water surface and horizontal bending in the plane of the water surface. The latter is due to the "snaking" of the hose-string. The analysis of the model test data is based, for the most part, on spectral analysis techniques. The experimental work is augmented by theoretical analysis. Considering the heave, surge and pitch of the buoy as uncoupled s.d.o.f. systems leads to models for the prediction of the SBM's response in waves. Analytical models, based on engineer's bending theory, are developed for the prediction of the vertical and snake-induced horizontal bending moments along the hose-string. Conclusions are reached regarding the response of the CALM buoy in waves and the dependence of vertical bending, horizontal bending and axial loads on the waves and buoy motions.