Effects of buoyancy modules geometry on hydro-elastic and hydrodynamic performance of a steep wave riser in steady current

• Published in: Volume 5A: Pipeline and Riser Technology
• Main Authors: Calvert, SJ, Balash, C, Chai, S, Izarn, C, Morand, H
• Format: Conference Object
• Language: English
• Published: American Society of Mechanical Engineers 2015
• Subjects: Engineering; Maritime Engineering; Ocean Engineering; Arctic
• Online Access: http://proceedings.asmedigitalcollection.asme.org/ConferenceProceedings.aspx; https://doi.org/10.1115/OMAE2015-41336; http://ecite.utas.edu.au/101237

Analysis of the hydrodynamic properties and response offlexible risers in various configurations is paramount tounderstanding their operative performance. Buoyancy modulesplay an integral role in providing compliance to flexible risersystems in wave configuration. This study utilised both modeltesting and numerical simulations to quantify the impact ofdiscretised and smeared buoyancy module sections on theperformance of a flexible riser in shallow water steep waveconfiguration under steady current loading. Model testing wasfacilitated in the Australian Maritime Colleges CirculatingWater Channel by a 1:15 scale 8 flexible riser constructedfrom silicon hose and foam. Variances in the models buoyancymodule section and system offset were tested at different flowvelocities to estimate the effect on in-line drag and top tension,and the change in curvature radius experienced by the riser.The tested systems were also modelled in dynamic analysissoftware for comparative purposes, where industryrecommended practices were employed to specify dragcoefficients. Numerical simulations exhibited an appreciablyhigher in-line drag compared to model testing results at higherflow velocities. Comparison of curvature radius resultsdemonstrated close agreement at lower flow velocities, withnumerical simulations exhibiting increased deformations due tothe higher in-line drag estimated at higher flow velocities. Thisdiscrepancy might be partially attributed to an overestimationof drag coefficients defined within industry recommendedpractices. The findings from this study have shown thesignificance of utilising scale model testing to quantify thehydrodynamic responses of a flexible riser, and facilitate a basisfor further work which might provide additional insight into thediscrepancies between analytical modelling and scale modeltests.