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Feasibility study of a procedure to evaluate the effects of breadth without floats occurring in the connection between two drilling riser joints in the VIV phenomenon


In the last decade many deep and ultra deep waters reservoirs were discovered. Nowadays, some of these reservoirs are being explored and have demanded increasingly sophisticated drilling rigs, as well as long drilling risers. In this scenario, drilling risers become a critical equipment. Once oversized it can eventually inviable the operation due to the great weight, requiring bigger platforms to assure the safety of the operation. In this sense, a great effort has been done in order to predict more accurately the behavior of these structures. One of the forces to which these structures are subjected to is the vortex induced vibrations (VIV), that not only increase the risers fatigue damage, but also causes the drag amplification. Currently, SHEAR7 software can be considered as the benchmark in VIVs predictions. However, there are still gaps in improving this software, as pointed out by the technical literature. One of the shortcomings relates to riser sections with floats. Generally, in the coupling between the risers joints, there is a region without floats, causing "free ends" which induces three-dimensional flow. In this sense, this proposal aims to quantify the improvement caused by using hydrodynamic coefficients considering the "free ends" effects caused by the gaps in the drilling risers. For this purpose, some experiments will be held, considering only one environmental condition, so that the hydrodynamic coefficients, such as lift and drag coefficient, Strouhal number and data to enable the resolution of hydrodynamic damping, can be estimated. These coefficients are inserted into SHEAR7 software. A real drilling riser condition is going to be simulated in SHEAR7 and the results will be compared with the measured data, to be possible to quantify the improvement caused by the use of hydrodynamic coefficients obtained in this project. (AU)

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