ESTIMATION OF FLEXIBLE CYLINDER DISPLACEMENTS IN WAVE-BASIN EXPERIMENTS

This paper describes a method developed to estimate the three-dimensio nal displacement field of long, flexible cylinders subjected to wave l oading. The method makes use of the relationship between curvature and displacement of a uniform beam. The technique was implemented in a la rge-scale experimental study to investigate the response of a pair of flexible cylinders in close proximity, with an emphasis on the collisi on behavior between them. The model cylinders were designed to be repr esentative of risers or tendons of a tension-leg platform in approxima tely 1000 m of water, The cylinder models, approximately 17-m long and 0.03-m diameter, were instrumented to measure the cylinder curvature at discrete locations along their length, At each time step the displa cement field was computed from the curvature measurements using a 'sho ot-to-fit' numerical-integration scheme. This procedure yielded a comp lete description of displacement along the cylinder as a function of t ime. The number and location of the curvature measurements were optimi zed by simulating the wave-flexible cylinder interaction with a finite -element model that was also used to demonstrate the accuracy of the m ethod. The effectiveness of the technique is demonstrated by results f rom the experimental program, and it appears to be feasible to adapt t his approach for field experiments.