Riser Interaction Model: A Combined T/F Domain Model

The primary object of this research investigation was the development of a new analysis approach to the hydrodynamic modeling of complex fluid-structure interaction phenomena, such as the hydrodynamic interaction of closely spaced risers subject to design seas. Because of the complex nature of the problem, a combined time/frequency domain approach was selected as the basis for the analysis. The next logical steps in the development of this methodology were motivated by the need in offshore design to more precisely address the frequency dependence of key parameters such as added mass, stiffness and damping, as well as, the need to exploit the advantages of using fully correlated signals in the process of design parameter estimation. Based an understanding of the analysis requirements and the initial interpretation of some existing multiple riser data, it was concluded that a suitable data set for marine risers was not available. Consequently, other test data sets were considered for possible use and it was determined that it would be possible to utilize a series of recently performed model tests involving complementary model tests of a rigid hull model and its compliant platform counterpart. The reverse system identification model has been developed; it can be applied to investigate complex hydrodynamic aspects of marine riser and floating platforms systems. The final objective was to clearly document some of the subtle aspects of the methodology for successful application and interpretation of practical problems. This project has been completed.