Tandem Riser Hydrodynamic Tests at Prototype Reynolds Number Available to Purchase

Deepwater riser interference is an area of significant technical complexity and uncertainty in the design cycle due to the intricacies of wake hydrodynamics. Existing models, found in industry guidelines, are based on approximate theoretical models of bare cylinder wake and nominally checked against small scale tests at low Reynolds numbers. In actual conditions the Reynolds number is sufficiently higher and the risers are fitted with vortex-induced vibration (VIV) suppression devices. This raises questions on the applicability of the standard models and hydrodynamic coefficients used, especially if the geometry is different than a circular cylinder. A series of full scale tests, at supercritical Reynolds numbers, were conducted to address these uncertainties and obtain hydrodynamic coefficients for interference design. The tests were carried out utilizing two full scale cylinders fitted with actual VIV suppression devices and towed either in fixed or spring supported configurations. The paper discusses the experimental methodology and findings from the testing program, showing deviations from the standard models found in industry codes.