Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1977. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 114-116. / M.S.

Ship-shaped hulls have often been found to be subject to excessive roll motions, and therefore, inhibit their use as a stable production platform. To solve the problem, bilge keels have been widely adopted as an effective and economic way to mitigate roll motions, and their effectiveness lies in their ability to damp out roll motions over a range of frequencies. In light of this, the present research focuses on roll motions of shipshaped hulls. A finite volume method based two-dimensional Navier-Stokes solver is developed and further extended into three dimensions. The present numerical scheme is implemented for modeling the flow around ship-shaped hulls in roll motions and for predicting the corresponding hydrodynamic loads. Also conducted are studies on the hydrodynamic performance of ship-shaped hull sections in prescribed roll motions and in transient decay motions. Systematic studies of the grid resolutions and the effects of free surface, hull geometries and amplitude of roll angle are performed. Predictions from the present method compare well to those of other methods, as well as to measurements from experiments. Non-linear effects, due to flow viscosity, were observed in small as well as in large roll amplitudes, particularly in the cases of hulls with sharp corners. The study also shows that it is inadequate to use a linear combination of added-mass and damping coefficients to represent the corresponding hydrodynamic loads. As a result, it also makes the calculation of the hull response in time domain inevitable. Finally, the capability of the present numerical scheme to apply to fully three-dimensional ship motion simulations is demonstrated. / text

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

No description available.

Approved for public release; distribution is unlimited. / The USS Winston S. Churchill (DDG-81) shock trial was conducted in May and June of 2001 off the coast of Naval Station Mayport, Florida. Because the USS Winston S. Churchill best represented the new line of Flight II-A Arleigh Burkes, it was chosen to undergo ship shock trials for its class. These trials are necessary in order to evaluate the vulnerability and survivability of the hull and the mission essential equipment in a "combat shock environment". However, shock trials are very expensive, require extensive planning and coordination, and represent a potential hazard to the marine environment and its mammals. Computer modeling and simulation are showing themselves to be a plausible alternative in investigating the dynamic response of a ship under these shock trials conditions. This thesis investigates the use of computer ship and fluid modeling, coupled with underwater explosion simulation and compares it to actual shock trial data from the USS Winston S. Churchill. Of particular concern in this study is the amount of fluid that must be modeled to accurately capture the structural response of a full ship finite element model. Four fluid meshes were constructed and used to study the ship's response to an underwater explosion. Each simulation data was analyzed to determine which mesh best represented the actual ship shock trial results. / Lieutenant, United States Navy

The use of surface piercing propellers (SPPs) shows promise for high speed operation by virtually eliminating appendage drag, which can be as much as 30 percent of the total drag on a vehicle at high speeds. The scarcity of available systematic test data has made reliable performance prediction difficult. The primary objective of this research is to obtain experimental performance prediction data that can be used in SPP design. In a series of open water tests in a non-pressurized towing tank facility, force transducer measurements were taken at tip immersion ratios from 0.5 to .33, yaw angles from 0° to 30° and inclination angles from 0° to 15° over a range of advance ratios from 0.8 to 1.8. Force transducer measurements were taken for thrust, torque, side forces and moments. These results will help develop a baseline for the verification of SPP performance prediction. / by Justin M. Lorio. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Naval submarines and surface ships are regularly subjected to a treatment called &quotdeperming&quot that seeks to design the vessel???s permanent magnetisation for optimal magnetic camouflage. A scaled model of a magnetic treatment facility (MTF) has been established as a valid system to simulate deperming and used to investigate various aspects of the deperm process including: magnetic anisotropy and demagnetising fields as factors in the physical modelling of magnetism in whole vessels; a comparison of current and alternative deperm procedures; the application of theoretical models of bulk magnetisation to calculate deperm outcomes in the physical model and in actual vessels. A &quotlaboratory MTF&quot was constructed to imitate the applied field geometry at a naval MTF. The system was calibrated and it was determined that the laboratory MTF could make magnetic measurements on a CU200T-G steel bar sample with an equivalent accuracy (error = ??5%) to that of standard magnetometric equipment. Experiments were conducted with emphasis on a holistic approach to modelling the deperm process and describing magnetisation changes in whole objects. The importance of the magnetic anisotropic changes to steel with cold rolling was confirmed. In CU200T-G steel sheet the initial susceptibility (ci) was found to increase by a factor of 3 ??0.1 in the rolling direction, from a value of ~ 110 in the un-rolled steel sheet (thickness dependent). ci in the rolled sheet transverse to the rolling direction was decreased by a factor of 0.94 ??0.09 to ci in the un-rolled sheet steel. Previous studies on hull steel have neglected to account for this transformation through cold work. The demonstration on mild steel here is expected to have an analogy in the final state of the hull sheet steel as it resides in a submarine pressure hull. Future studies either on hull material or on modelling whole vessels should include the same or similar magnetic anisotropic properties in the steel(s) under investigation. Hollow circular tubes made from CA2S-E and CU200T-G steel sheet were selected as models for vessels. It was shown that these steel tubes were a good choice in this regard: minimising the complexity of the experiment whilst maintaining the validity of a deperm simulation. During a deperm there was an excellent qualitative likeness in the permanent longitudinal magnetisation (PLM) for the steel tubes to PLM in both a submarine and a surface vessel. Permanent vertical magnetisation (PVM) deperm results from the tubes displayed a close qualitative match with PVM in a submarine but not in a surface vessel. A theoretical treatment for demagnetisation factors (Nd) in hollow ellipsoids was used in conjunction with a geometrical approximation to calculate Nd for finite hollow objects of revolution. Subsequent theoretical calculations correlated well with experimental results for measured effective ci (ceff) in hollow circular CU200T-G steel tubes of various lengths and aspect ratios. Using an estimate of 100 as ci for submarine hull steel, the same analysis produces Nd for the axial and transaxial directions in a submarine equal to 5.97??10-3 and 0.0142 respectively. Three items for potential improvement were identified in the current deperm protocol used on naval vessels (Flash-D): redundancy in the protocol; the duration of the deperm and a theoretical basis for predicting the final magnetisation or changes in magnetisation during a deperm. Simulations of a novel &quotanhysteretic deperm&quot method, designed to combat these issues, compared favourably to the Flash-D protocol. The standard deviation (s) of the final PVM from 30 Flash-D deperms on steel tubes was 206 A/m; for the final PVM from 30 anhysteretic deperms of the same duration, this was 60 A/m. The s for the final PLM for Flash-D and anhysteretic deperms of the same duration were 416 A/m and 670 A/m respectively. The conclusion is that adopting the anhysteretic deperm on actual vessels would improve the reliability of the PVM outcome. Though the procedure would demand the same duration as Flash-D, there is the advantage of saving time by not having to repeat deperms to obtain the desired result. Additionally the anhysteretic deperm is considerably more amenable to theoretical analysis. A modified version of Langevin???s equation was used to predict the final PLM and PVM results for anhysteretic deperms and to provide a useful analysis of the anhysteretic processes in the Flash-D procedure. Using a Preisach analysis of hysteresis, a mathematical description of bulk magnetic changes that occur to a specific object, within a deperm, has been developed. Theoretical calculations of PLM in a steel tube during and after both types of deperm are in excellent agreement with experimental data. The same theoretical approach was also used to retrospectively model PLM results from previous Flash-D deperms on a submarine with equal success. With this analysis it is proposed that anhysteretic deperm outcomes could be predicted a priori. The influence of magnetic cargo on hull magnetisation was demonstrated to be of significance during and after deperming. &quotSympathetic deperming&quot occurs where a magnetic source is located close to the hull during a deperm. It was found that a vessel or model vessel hull could still be demagnetised even when they contain magnetic cargo that would normally resist the direct application of the same magnetic fields. This was explained using the principles of demagnetising fields and anhysteretic magnetisation. A possible explanation was provided for a PVM measurement anomaly common to the model and vessel deperm results. From measurement, alternating longitudinal applied fields apparently induce corresponding changes in the PVM. This effect could be explained by the depermed object being offset longitudinally from the position expected by the measurement system. This offset could be estimated using an analysis of the changes to PLM and PVM after a longitudinal applied field. The offset displacements calculated for the vessels were too small to be verified experimentally (&gt 0.1m), but the predicted offset for the steel tubes coincided with the limit of precision for their placement in the laboratory MTF = 0.5mm The aim of this work was to look at the deperm process with reference to a system that demonstrated qualitative similarities to deperms on actual vessels. The laboratory MTF is a unique facility, permitting a useful practical analysis of deperming based on sound magnetostatic measurements The experimental and theoretical results gained here have direct application to future deperms on naval vessels with particular reference to submarines.

The present research investigates nonlinear barge motions through analyses of coupled multi-degree-of-freedom (MDOF) deterministic and stochastic models. Roll-Heave-Sway and other lower-ordered models are developed to predict the nonlinear motions and analyze the stability of a class of ship-to-shore cargo barges. The governing equations of motion contain coupled rigid body Roll-Heave-Sway relations, hydrostatic and hydrodynamic terms. The rigid body relationships are a part of the general six-degree-of-freedom model. Hydrostatic terms include effects of the barge's sharp edge and of relative Roll-Heave states. Hydrodynamic terms are in a "Morison" form. The characteristics of the excitation wave field are based on linear wave theory. Predictive capabilities of the Roll-Heave-Sway and the Roll-Heave models are investigated. System parameters are calibrated to match experimental test results using several regular wave test cases. Potential theory predictions provide initial estimates of several key system parameters. With the identified system parameters, numerical predictions obtained from time domain simulations of both models are compared with experimental test results for a random wave case, and compared to each other to investigate the coupling effects of sway on roll and heave motions. Reliability against capsizing of a barge in random seas is investigated using stochastic analysis techniques. With the Markov process assumption, the barge response density to random waves is derived as a solution to the corresponding Fokker-Planck equation. The path integral solution technique is employed to obtain numerical solutions for the Roll-Heave and the Roll models. A quasi-2DOF model is introduced to improve the accuracy of the 1DOF Roll model. The reliability of a barge in a variety of sea conditions is analyzed as a first passage problem using the quasi-2DOF model. Mean times to reach specified capsizing probabilities for a barge operating in sea states 1 through 9 are obtained. / Graduation date: 2003

Taiwan is surrounded by ocean; shipping industry is well-developed in this island. Evergreen, Yang-Ming and Wang-Hai are very well-known and also big shipping company in the world. So the industry of ships machine parts should be very well-developed here in Taiwan, but truth is it not very well-developed here. The purpose of this study was to find out the rules when shipping industries purchase ships machine parts, also how they recognize the quality, brand and service of the products. The study used case methodology and interview to shipping industry in order to find out the reason why industry of ships machine parts was not well-developed here in Taiwan. Hope the results of the study could made some efforts to future studies.