A Computer Aided Method for Preliminary Design of SWATH Ships

MacGregor, James R (1989) A Computer Aided Method for Preliminary Design of SWATH Ships. PhD thesis, University of Glasgow.

Abstract

This thesis describes a computer aided method for integrating the preliminary design and hydrodynamic analysis of SWATH ships. A considerable quantity of data for use in the design of these vessels is also provided. The thesis begins with a brief outline of the development history and the advantages and disadvantages of the SWATH concept. Some difficulties associated with the efficient design and operation of SWATH ships are described. A related need for integrating advances in hydrodynamics with a means of producing balanced designs is identified. A large collection of SWATH design data is presented and analysed. Several well defined expressions relating principal vessel dimensions are identified and proposed as aids in initial design. Current practices in the fields of ship design and computer aided engineering design are reviewed. These aspects are discussed with particular reference to SWATH design. From this background, an approach to the design of SWATH ships with computer assistance is developed. A number of methods for the initial sizing of SWATH ships are developed. These are; a computer database, a mini-synthesis program, a weight equation approach, and manual approaches based on curves relating SWATH size to desired seakeeping characteristics, payload weight and/or volume, deck area and enclosed volume. These are designed to increase the efficiency of more complex synthesis tools. The development and validation of a method for hull definition and associated hydrostatic analysis is described. This is a necessary link between simple geometry definitions and those required for full synthesis including hydrostatics, resistance, seakeeping, and graphics. A family of SWATH designs produced by this tool is introduced as a basis for parametric studies. A review is made of available methods for predicting the resistance of SWATH ships. The integration of these techniques with the synthesis model is described and results of some comparative and parametric studies presented. Methods currently used in preliminary design of propellers for SWATH ships are reviewed and a collection of model test data is presented. The available data is used to develop expressions relating self propulsion factors to basic design parameters. These are integrated with the open water characteristics of Troost B-series propellers in a computer program. A study of the propulsion aspects of a family of typical SWATH designs is presented. The machinery options available to the SWATH designer are considered. A collection of relevant data is provided as a basis for power plant selection and weight estimation, and a computer model to aid in SWATH machinery design is described. Results from studies carried out using this tool are used to illustrate important factors in this aspect of SWATH synthesis. Limiting powers and speeds are identified for a wide range of prime movers and hullforms. A method for estimating SWATH ship structural weight is developed. Design for primary wave loading and slamming impact is considered. The validation of this tool and its use in parametric studies is described. Data is provided to assist in the preliminary arrangement of structure and its weight estimation. A regression analysis performed on a collection of data is used to develop a parametric method for weight estimating. The development of a generalised computer program for estimating the space requirements of escort warships is also described. These weight and space routines are applied to the design of SWATH escort vessels and a strong conflict between space and weight demand is identified. The importance of vehicle density in balancing SWATH designs is illustrated. Some additional systems which provide greater design definition are briefly discussed. In particular, a graphics interface and link with a 3D motions and loading program are described. The use of the SWATH design method is illustrated by means of examples. The application of the procedure to two conceptual SWATH designs for the UK MoD and the design of the first SWATH ship to be constructed in the UK is described.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Naval engineering
• Date of Award: 1989
• Depositing User: Enlighten Team
• Unique ID: glathesis:1989-77806
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jan 2020 11:53
• Last Modified: 14 Jan 2020 11:53
• URI: https://theses.gla.ac.uk/id/eprint/77806