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An Analysis of the Loads on and Dynamic Response of a Floating Flexible Tube in Waves and Currents

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Trident Scholar Project rept. no. 427

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Proposed offshore structure designs for algal production using wastewater may incorporate floating flexible tubes. This study includes an extensive set of physical modeling experiments to investigate the loads on and dynamic response of these tubes in waves and currents. The physical modeling approach involved designing and building an approximately 14 scaled representation of a potential design. Experiments were conducted with the model in the 37-meter towwave tank in Hydromechanics Laboratory at the United States Naval Academy. Several combinations of model tests were performed in scaled waves and currents at tube fill levels of 50 and 95. Several of the tow tests done in the tank, representing oceanic currents, were validated with computational fluid dynamics. Along with the time series drag results, the physical modeling experiments that included both regular and random waves were analyzed to produce linear transfer functions for both heave and force. An assessment of these data sets indicated that the flexible floating tube response generally followed the wave forcing at the middle wave frequencies. For both fill levels, the response of the forward end of model increased with wave frequency while the response of the rear end of the model remained rather consistent across the frequencies tested. The results did not indicate a significant difference in dynamic response when the model was tested in both waves and current. The average attachment loads, however, were higher when the model was tested in waves and a current than in waves only.

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  • Fluid Mechanics

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