THE USAGE OF ARTIFICIAL NEURAL NETWORKS IN HYDRODYNAMIC ANALYSIS OF FLOATING OFFSHORE PLATFORMS
Floating offshore structures, particularly floating oil production, storage and offloading systems (FPSOs) are still in great demand, both in small and large reservoirs, for deployment in deep water. The prediction of such vessels’ responses to her environmental loading over her lifetime is now often undertaken using response-based design methodology, although the approach is still in its early stages of development. Determining the vessel’s responses to hydrodynamic loads induced by long term sea environments is essential for implementing this approach effectively. However, it is often not practical to perform a complete simulation for every 3-hour period of environmental data being considered. Therefore, an Artificial Neural Networks (ANN) modelling technique has been developed for the prediction of FPSO’s responses to arbitrary wind, wave and current loads that alleviates this problem. Comparison of results obtained from a conventional mathematical model with those of the ANN-based technique for the case of a 200,000 tdw tanker demonstrates that the approach can successfully predict the vessel’s responses due to arbitrary loads.
A novel approach for motion predictions of a semi-submersible platform with neural network
A neural-network-based prediction of motion responses of a semi-submersible is presented here. The fully connected neural networks and the long–short-term memory networks were employed to establish the neural networks for motion predictions. The effects of network architectures and time steps were investigated in depth. The predicted results were compared with the measurements and the predictions based on other conventional methods. The results demonstrate that the neural-network-based approach could offer a fast and accurate prediction of heave, roll, and pitch responses of a semi-submersible. This provides a promising alternative for evaluations of hydrodynamic performances of new designs and monitoring of the dynamic behavior of in-service floating structures.
HYDRODYNAMIC DESIGN OF MOORED FLOATING PLATFORMS
Single point moored floating production platforms provide an economically viable option for deep water marginal field oil and gas production. In the design of such systems, non-linear time domain analysis tools are required to predict the wave and low frequency motions and the mooring forces due to non-collinear wave, wind and current load actions. The authors of this paper have developed and validated with experimental measurements non-linear analysis tools to predict the dynamic motion response and mooring forces of a CALM system due to non-collinear environmental forces. In the first part of the paper a brief summary of the non-linear analysis procedure developed by the authors is given, together with some results obtained from predictions and experimental measurements. In the second part of the paper the results of parametric studies investigating the effects of variations in wave, wind and current magnitude and direction, wave and wind spectral shapes, the number of mooring lines, hawser length and stiffness, buoy size and thruster capacity on the steady and slowly varying oscillations of the CALM system and on mooring and hawser forces will be illustrated.