Experimental Investigation of Dual Riser Interaction

Hydrodynamic interaction and clashing of two long flexible cylinders in uniform steady current have been studied. Model tests have been performed in the towing tank at Marintek in Trondheim. The riser models were free to move in vortex induced vibrations (VIV) and wake induced vibrations (WIO). The main objectives of the experimental campaign were to acquire high quality data that can be used to enhance the understanding of the mechanisms that drives riser clashing and to provide benchmark data for riser clashing code validation. Model tests were performed both for straked and naked risers, and for risers with and without bumper elements attached. Riser spacing, inflow angle, riser pretension and current velocity were systematically varied. The analysis of the recorded data has emphasized on assessing the spatial distribution of clashing, the relative impact velocities, WIO and VIV.