A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in the fulfilment of the requirements for the Degree of Master of Science in Engineering. 1992 / The absence of reliable design data for Glass Reinforced Plastic (GRP) road tankers has been considered an obstacle for the local design and manufacture of such vehicles. This has prompted the analysis, using Finite Element Methods (FEM) of a filament wound cylindrical shell for a monocoque road tanker. [Abbreviated Abstract. Open document to view full version] / GR 2016

This thesis presents a new set of methods to assist the process of ship design for safety with particular reference to collision damage. The study has two principal objectives: " investigations into subdivision aspects of passenger ships to improve their overall survival index " investigations into the subdivision of oil tankers in order to improve the effectiveness against spillage in the event of collision damage. In order to investigate the ship subdivision aspect a damage stability model was needed. A pre-requisite for developing the damage stability software was a robust but flexible method to define the hull and the compartments of subdivision. B-splines have been a popular representationatl ool in computer aided design over the past three decades.T his method, though more complex than other spline techniques such as cubic splines, was adopted with a fourth order basis function in this work. A complete set of spline manipulation libraries and associated numerical solvers were developed for this purpose. In addition to this, a method to define the intersection between the hull and the waterplane in the form of a closed B-spline curve for any given orientation of the vessel in terms of -heel, trim and draught was developed to aid the damage stability calculations. Though the earlier regulations stipulate fixed trim assessments to ease the computational process, it is clearly unsatisfactory and research has confirmed this to be a flawed approach. Free trim calculations on the other hand require an iterative and time consuming process to arrive at the equilibrium trim position for each heel angle. Pawlowski proposed a new method for the stability calculations of a freely floating rig when the unit is arbitrarily orientated to the wind direction. It uses the Euler theorem on the properties of equivolume waterplanes to arrive non-iteratively at the new inclined position. This theory was adapted for use in damage stability calculations and was numerically tested and proved to be sound. Damage stability calculations, though combinatorially large, are also inherently parallel. Parallel Virtual Machines (PVM) is a Message Passing Interface (MPI) developed jointly by ORNL, University of Tennessee, Carnegie Mellon University and the Pittsburgh Supercomputing centre. PVM enables a "virtual configuration" so that a collection of serial, parallel and vector processing machines appear as one large distributed memory computer. PVM was compared with another MPI called Network Linda where the advantage of PVM's user controlled message passing was demonstratedP. VM was used to implement the MJMD Distributed Memory paradigm to exploit this inherent parallelism in damage stability calculations and to obtain speedups. A systematic exploration of the search space for this design problem involves the generation of a large number of internal subdivision configurations. This, coupled with the fact that the design space was multimodal in nature made it suitable to the application of a class of heuristic search algorithms called Genetic Algorithms (GA). A brief description of the mechanisms behind GA is presented along with their mathematical basis in the form of two theorems: the schema theorem and the building block hypothesis. Various techniques for solving constrained optimisation problems with GA was explored. The penalty function method was found to be the most suitable and was finally adopted. The above techniques were applied to the optimisation. of the internal subdivision of passenger ships and cargo ships, oil tankers in particular. For passenger ships, the nature of the 's'-factor formulation on the local index was shown. The multimodal nature of the subdivision problem was highlighted and a GA was used to investigate the optimal subdivision characteristics of the vessel. The 's' factor formulation for cargo ship rules is different to that described by the A. 265 set of regulations for passenger vessels. In addition, the cargo ship rules describe a factor V which accounts for the probabilities of vertical extents of damages. However this formulation does not assign any credit for horizontal subdivision below the waterline. Data on vertical extents and vertical location of damages for cargo ships was collected and analysed in earlier studies done at Newcastle University. This data was used to develop a probability function akin to that developed for the longitudinal extent and longitudinal location so as to give credit for any horizontal subdivisions. The principal objective of this part of the study was to explore the search space for subdivision configurations that would minimize net oil outflow.

This thesis presents an in-depth study of the gas freeing of marine crude oil tanks using numerical simulation, beginning with a general summary of the problem, followed by an outline of the objectives of this work and the main difficulties involved. To outline essential background, a review of numerical methods, fluid flow, and related physical mechanisms has been undertaken, in addition to related ventilation fields, jet and jet impingement, and tanker-borne ventilation, in order to determine the state of the art and draw useful parallels between different ventilative fields, as well as identifying potential areas for model validation. A room-ventilation test case was studied in order to demonstrate the numerical method. It was found that assuming adiabatic walls and ignoring radiation resulted in highly idealised temperature predictions, and that radiation played a large part in enhancing vertical temperature prediction by redistributing thermal energy. For the gas-freeing analysis, the geometric models and solution procedures are introduced before simulation results presented and validated with analytical jet models and impingement penetration parameters. Analysis showed that the internal temperature of the tank was approximately homogeneous, allowing the tank to be considered isothermal. 2D simulations showed that after an initial period of time, the relative concentration distribution reaches steady state with decreasing average concentration as gas-freeing continues. Discussion of the results followed, examining aspects surrounding heat transfer and the choice of turbulence model, analysing the differences in the results between the first and secondmoment closure schemes and justification of assuming isothermal conditions. The variation in concentration was examined, and an analytical expression was derived which approximates the reduction in average gas concentration decay due to gas-freeing. It has been shown that double-hulled construction renders the internal temperature variation to around 10% of the temperature difference between the sea and deck. During the gasfreeing process proper, it was shown that after any stratified layer has been eroded and a stable flow field established, the relative concentration distribution remains constant. Gas freeing times were shown to be heavily dependent on the volume flux (and thus air change rate), and mathematical relations derived in order to provide approximately predict the time to gas free a crude oil tank (COT) given particular initial conditions.

No description available.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / Microfiche copy available in Archives and Engineering. / Includes bibliographical references. / by George Economou. / M.S.

Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Diane B. Greene. / M.S.

Thesis (M.A.)--Ohio State University. / Includes bibliographical references (leaves 89-92). Available online via OhioLINK's ETD Center

21, [58] leaves : ill. ; 28 cm.

The oil tankers that operate on the Trans-Alaska Pipeline Service (TAPS) route have exhibited a large number of structural fatigue cracks. These cracks can be attributed to the increase in use of high strength steel in tanker construction and to the harsh operating environment in the Gulf of Alaska. In response to the TAPS fatigue problem, this project examines the topic of preliminary design for fatigue resistance. The TAPS tankers have previously been the target of several studies on the subject of fatigue cracking. Most of these studies have concentrated on reducing the costs and risks involved with operating the current tanker fleet. Preliminary design, however, is oriented at reducing the fatigue risk in future tanker designs. To that end, the design method outlined within concentrates on the level of analysis that is appropriate for preliminary design. The design method consists of four steps: the specification of a wave environment, generation of a hydrodynamic model and subsequent wave loads, evaluation of cyclic stresses and an assessment of fatigue damage. A series of example calculations that is typical of preliminary design has been performed for one of the TAPS tanker classes. These calculations employed Buckley's climatic wave spectra, a 3-dimensional panel based hydrodynamics package by Lin and a Miner's rule fatigue assessment based on the S-N curves of the British Welding Institute. The example calculations yield two important results. First, relatively inexpensive methods can yie1d important and accurate fatigue results; for a side shell longitudinal at the water line the example calculations predict a fatigue life of approximately 3 operating years. This corresponds quite well to the published inspection data and obviously represents insufficient fatigue life. Second, local panel pressures can have a significant contribution to, and even dominate, total fatigue damage in the side shell. This contrasts with conventional fatigue studies of ship hulls which focus on global loads; i.e., hull girder bending. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (M.S.)--Joint Program in Marine Environmental Systems, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1998. / Includes bibliographic references (p. 79). / by Charles E. Rawson. / M.S.