Flat Buoy Concept for Free Standing Riser Application: An Improvement of the In-Place Hydrodynamic Behaviour

Abstract

The study focuses on the in-place hydrodynamic behavior and Flow Induced Response of a novel design of Free Standing Riser (FSR) system tensioned by a ‘Flat-Buoy’. The paper presents results review of both Experimental and Numerical approaches initiated in the framework of a comprehensive Research & Development program. Experimental and numerical study conclusions converge on the excellent hydrodynamic Stability of such FSR system. First, wind tunnel campaign, based on Reynolds similitude, has focused on the flow features over the fixed Flat Buoy. No Vortex Shedding has been clearly highlighted. Moreover, results have pointed out a more pronounced dependence of the hydrodynamic coefficients to the flow incidence than to the Reynolds number. Secondly, basin model tests, based on Reduced Velocity similitude, have highlighted the stability of such scaled FSR system concluding to maximum Cross-Flow and In-Line amplitude such as A/D<0.35 (A represents the amplitude and D the Buoy diameter). In parallel, hydrodynamic stability has been investigated Benchmarking Computational Fluid Dynamic (CFD) methods. Preliminary validation steps have pointed out ability of such CFD approaches to globally predict both Wind Tunnel and Basin Test results. Finally, extending CFD and Fluid Structure Interaction (FSI) modeling to full-scale configuration, stability of the FSR tensioned by a Flat-Buoy has been proved.

Numerical Investigation on Hydrodynamic Characteristics of Immersed Buoyant Platform

“…Five different cases were simulated with mesh numbers of approximately 150,000, 300,000, 600,000, 1,200,000 and 2,400,000. The simulated results which include computational time, comparison of the time averaged drag coefficient between simulations and experiments [27,28], relative error are exhibited in The simulated results which include computational time, comparison of the time averaged drag coefficient between simulations and experiments [27,28], relative error are exhibited in Table 1, Figures 4 and 5. The results demonstrate that the relative error decreases as the mesh number increases, while the computational time increases significantly with increasing mesh number.…”