UBC Theses and Dissertations
Maximum scour around cylinders induced by wave and current action Abusbeaa, Abubaker Mohamed
The maximum possible scour around cylindrical structures under the action of combined wave and current was investigated in this study. A review of the literature showed that there are no adequate theories or methods for predicting maximum possible scour depths around structures under the action of wave plus current. Development of such a scour prediction is of considerable economic importance for the design of offshore structures. The study started with experimental tests of the scour around cylindrical structures and a comparison was made between scour under steady currents alone, waves alone and combined wave and current conditions. Existing theories for scour and flow velocities under waves alone and currents alone were analyzed and sets of experiments were performed for the three flow conditions of waves alone, currents and waves plus currents using three sediment size ranges and five cylinder sizes. The dependence of maximum scour on both cylinder size and sediment size for the three flow cases was studied and graphical relationships were established. The maximum scour under combined wave and current at threshold conditions in the approaching flow was investigated in detail and the dependence of maximum scour on this critical threshold flow criterion was shown. The maximum scour depth can be roughly estimated using this study provided that the flow conditions, sediment properties and structure dimensions are defined.
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