Browsing by Subject "Ship"
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Item Fender system behavior in random seas(2009-05-15) Ofoegbu, James NwachukwuFendering systems are widely used in offshore installations for attenuating the effects of the impact energy of ships and barges in berthing or moored conditions. This study focuses on investigating current design practices and, developing a rational and functional approach to address random loading effects exerted on fendering systems. These loadings are often a consequence of combined wind, wave and current excitation as well as more controlled vessel motions. Dimensional analysis is used to investigate the degree to which empirical design data can be collapsed and to provide an indication of the nonlinearity associated with the empirical data for fender sizing. In addition, model test data specifically measuring the normal fender force for a coupled mini-TLP/Tender Barge performed at the Offshore Technology Research Center (OTRC) model basin is used in this research investigation.. This data was characterized in terms of the typical statistical moments, which include the mean, standard deviation, skewness and kurtosis. The maxima and extreme values are extracted from the fender response data based upon a zero-crossing analysis and the results were studied in order to determine the underlying probability distribution function. Using selected parameter estimation techniques, coefficients of a best-fit two parameter model were determined. An illustrative example is presented and discussed that contrasts the deterministic and probabilistic models.Item Hybrid powertrain performance analysis for naval and commercial ocean-going vessels(2012-08) Gully, Benjamin Houston; Seepersad, Carolyn C.; Webber, Michael E., 1971-; Hebner, Robert E.; Kiehne, Thomas M.; Chen, DongmeiThe need for a reduced dependence on fossil fuels is motivated by a wide range of factors: from increasing fuel costs, to national security implications of supply, to rising concern for environmental impact. Although much focus is given to terrestrial systems, over 90% of the world's freight is transported by ship. Likewise, naval warfighting systems are critical in supporting U.S. national interests abroad. Yet the vast majority of these vessels rely on fossil fuels for operation. The results of this thesis illustrate a common theme that hybrid mechanical-electrical marine propulsion systems produce substantially better fuel efficiency than other technologies that are typically emphasized to reduce fuel consumption. Naval and commercial powertrains in the 60-70 MW range are shown to benefit substantially from the utilization of mechanical drive for high speed propulsion; complemented by an efficient electric drive system for low speed operations. This hybrid architecture proves to be able to best meet the wide range of performance requirements for each of these systems, while also being the most easily integrated technology option. Naval analyses evaluate powertrain options for the DDG-51 Flight III. Simulation results using actual operational profile data show a CODLAG system produces a net fuel savings of up to 12% more than a comparable all-electric system, corresponding to a savings of 37% relative the existing DDG-51 powertrain. These results prove that a mechanical linkage for the main propulsion engine greatly reduces fuel consumption and that for power generation systems requiring redundancy, diesel generators represent a vastly superior option to gas turbines. For the commercial application it is shown that an augmented PTO/PTI hybrid system can better reduce cruise fuel consumption than modern sail systems, while also producing significant benefit with regard to CO2 emissions. In addition, using such a shaft mounted hybrid system for low speed electric drive in ports reduces NOx emissions by 29-43%, while CO is reduced 57-66% and PM may be reduced up to 25%, depending on the specific operating mode. As an added benefit, fuel consumption rates under these conditions are reduced 20-29%.Item The effects of wave groups on the nonlinear simulation of ship motion in random seas(Texas A&M University, 2006-04-12) Richer, Jeffrey A.Historically, the analysis of ship motion and loading responses has been performed in the frequency domain with both linear response amplitude operators and wave energy density spectra. This method, therefore, did not account for the nonlinear nature of waves. A more precise method is to obtain the response in the time domain, processing non-linear wave data with a linear response amplitude operator. Since the input is non-linear, even though the system is linear, the output will also be non-linear. This resultant data can then be used to generate a more accurate design of seaworthy vessels. Furthermore the linear frequency domain method does not account for the presence or effects of wave groups. This study shows the improved accuracy in the response obtained by accounting for non-linearities and furthermore indicates that wave groups affect the vertical relative motion of a moored ship (zero-speed).Item The evolution of decorative work on English men-of-war from the 16th to the 19th centuries(Texas A&M University, 2005-08-29) Steere, Alisa MicheleA mixture of shipbuilding, architecture, and art went into producing the wooden decorative work aboard ships of all nations from around the late 1500s until the advent of steam and the steel ship in the late 19th century. The leading humanists and artists in each country were called upon to draw up the iconographic plan for a ship??s ornamentation and to ensure that the work was done according to the ruler??s instructions. By looking through previous research, admiralty records, archaeological examples, and contemporary ship models, the progression of this maritime art form can be followed.