Session: 06-03-01 Fluid-Structure, Multi-body and Wave-body Interaction I

Paper Number: 101645

101645 - Environmental Loading on a Concrete Gravity-Based Offshore Structure in the Presence of Freak Waves and Currents 

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 (CGS) are described both on its shaft and topside. As numerical tools for simulating loads on the structure, OrcaFlex^TM, a commercial code, and a 3D mass, momentum, and energy model, are all utilized.

A 3D non-linear time-domain finite element implicit and explicit program called OrcaFlex^TM uses lumped mass elements to streamline equations, allows for diffraction, and speeds up computation. The properties of the wave-current field are described by the 3D numerical model using mass, momentum, and energy flux conservation equations. To explore numerous instances and compare data between the two numerical simulators, settings for incident wave conditions are systematically changed in the simulations. The CGS's geometry and still water depth 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 CGS design process and hence improve structural and operational safety in the severe and wave-current coexistence environment.

Presenting Author: M Hasanat Zaman National Research Council Canada

Presenting Author Biography: Dr. Zaman is a Research Engineer at The National Research Council of Canada since 2001. His research field is of ocean hydrodynamics for various scenario. He has been widely involved in numerical and physical modeling of waves, currents and ice dynamics.

Authors:

M Hasanat Zaman National Research Council Canada
Ayhan Akinturk National Research Council Canada