Multi-hull vessels have been considered for high-speed, military and commercial applications for decades. More recently the trimaran vessel, with three hulls, has captured interest among naval ship designers and stakeholders. A definition of multi-hulls is introduced as a continuum with monohulls on one end, catamarans on the other, and trimarans in-between. A review of methods to assess intact and damaged stability follows in addition to an overview of current research in the area of dynamic stability for monohulls and trimarans. An investigation of intact stability characteristics for multi-hulls along the continuum is presented and their trends are examined. Next, a series of trimaran configurations are modeled in CAD with subdivision to determine their allowable KG according to USN deterministic criteria and using quasi-static methods. A response surface model was determined for allowable KG as a function of center hull length to beam, side hull beam to draft, transverse position, and displacement for use as a rule of thumb measure and potential optimization constraint. / Master of Science / Ships which have more than one hull are called multi-hulls. In contrast to a monohull, which comprises of a single hull form, catamarans, trimarans, quadramarans, and pentamarans consist of two, three, four, and five hulls respectively and make up the multi-hull group of ships. Multi-hulls have been considered for high-speed, military and commercial applications for decades. More recently trimaran ships, with three hull forms, have captured interest among naval ship designers and stakeholders. This thesis provides a definition of multi-hulls as a continuum with monohulls on one end, catamarans on the other, and trimarans in-between.
An assessment of ship stability quantifies a ship’s risk of capsize in a particular loading condition and environment. The intact ship condition is assessed as well as damaged ship conditions where the certain compartments are subject to flooding from the sea. Initially, a quasi-static method is first undertaken where the ship characteristics are computed at discrete motion points of interest and integrated. This thesis includes a review of quasi-static methods employed by United States and British navies to assess intact and damaged stability. Additionally, an overview of current research in the area of dynamic stability for monohull and trimaran. Assessing stability using dynamic methods involves a more detailed assessment of extreme events a ship may encounter in its lifecycle. These assessments were beyond the scope of this thesis.
The first investigation of this thesis assessed the intact stability characteristics for multi-hulls along the continuum, including a monohull, five trimarans, and a catamaran. Trends were examined and the effect of displacement distribution between hulls on stability characteristics was analyzed. The results of the first investigation set the bounds for a more detailed investigation of trimaran geometric parameters affecting intact and damaged stability.
The second investigation established a design of experiments to formulate a series of trimaran configurations consisting of a center hull, two side hulls and cross deck structure joining the hulls from above. This series of trimaran hull forms varied particular parameters that were determined to be influential to intact and damaged stability. Each hull form configuration was modeled using three-dimensional CAD software with subdivision defining compartments to be flooded. The maximum center of gravity was determined which would satisfy all stability criteria published by the United States Navy for each intact and damaged condition. After tabulating the data, a response surface model was determined for maximum vertical center of gravity as a function of center hull ratios, side hull ratios, and the transverse distance between the center and side hulls. The response surface model is intended for use as a rule of thumb measure and potential constraint for optimization.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/81101 |
| Date | 08 December 2017 |
| Creators | Weidle, William Scott |
| Contributors | Aerospace and Ocean Engineering, Brown, Alan J., Brizzolara, Stefano, Bassler, Christopher Colby |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/x-zip-compressed |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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