| Abstract | There has been a rise in oil and gas industry activity in the offshore area of the North Seas as well as in other parts of the world. Operating offshore fixed and floating structures in such areas come with additional menaces due to the coexistence of large waves and strong currents and their consequent interactions. The effects of strong currents and large waves that move through the area may seriously impair the functionality and safety of these offshore structures, particularly when a large wave travels against a strong current since this could produce extremely high waves. In this study, the loadings of such a strong wave-current coexistence field on a concrete gravity based structure (GBS) are described both on its shaft and topside. The simulations use a 3D mass, momentum, and energy balanced model as numerical tools for predicting loads on the structure. Using mass, momentum, and energy flux conservation equations, the proposed 3D numerical model is formulated that describes the characteristics of the wave-current coexistence field. To study a variety of scenarios, incident wave and current conditions are systematically changed in the simulations. The local still water depth and the geometry of the GBS were maintained constant. The shaft has a diameter of 30m, and a length of 95m and the topside has a dimension of 50m towards incident wave direction, 75m in length, and 2m in depth. The still water depth is taken as 80m, and the estimated air gap is 15m. In each situation, the simulation lasts for three hours.
The new data and information that would be generated as a result of this effort may be vital for potential inclusion in the GBS design process and hence improve structural and operational safety in the severe and wave-current coexistence environment. |
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