Abstract
Solutions to the long-wave induced moored ship motion problems at the Port of Ngqura were investigated in this study. Long-wave mitigation options were modelled with various layout modifications to the present model of the port, which has been validated with measured data. The numerical model simulations were used to derive long-term data sets inside the Port. Several moored ship motion simulations, using alternative conventional and dynamic mooring options, were performed for an extreme wave and wind condition for each berth at the port. Preferred port layout options and optimal mooring solutions were then determined for each berth. A complete framework of wave and ship motion simulations were performed for the preferred mitigation options. The ship motions and mooring line forces were determined for the relevant vessels at selected berths. This allowed for berth operability and downtime statistics to be determined, taking the limiting wave height and allowable mooring line criteria into account. Since several port layout options and different mooring arrangements were assessed, a Multi-Criteria-Analysis (MCA) was followed to determine the best possible solution.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/y79b158riGE
Highlights
The Port of Ngqura is situated in Algoa Bay, about 20 km northeast of Port Elizabeth, South Africa
The two main groups or clusters of simulations refer to the pretension of the mooring lines
The results of the study indicated a general increase in operability with an increase in the pretension of the mooring lines, especially at the container terminal
Summary
The Port of Ngqura is situated in Algoa Bay, about 20 km northeast of Port Elizabeth, South Africa. A time series of modelled significant wave heights at 9 berth locations inside the port were analysed to determine the return conditions. This analyses illustrated the effect more extreme storm events would have on the different port layouts. This hydrodynamic file was generated using a panel model to represent the 3D shape of the ship hull, the quay and the sea bed and is based on 3D diffraction theory After this file has been obtained, quick computations can be carried out to determine the response in a different wave, current and wind condition or for different configurations of the mooring layout. The panel mesh is used by the 3D panel model, Wavescat to compute the hydrodynamic properties of the vessels as well as the wave force transfer functions
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