Date of Award

12-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean Engineering and Marine Sciences

First Advisor

Prasanta K. Sahoo

Second Advisor

Hamid Hefazi

Third Advisor

Ronnal Reichard

Fourth Advisor

Thomas. D. Waite

Abstract

Predicting the resistance of a high-speed catamaran has been of interest to naval architects for the last three decades. Even though considerable amount of research has been carried out in this area, there remains a degree of uncertainty in the accurate resistance prediction of catamaran hull forms in the early design stage. Researches carried out so far have generally ignored the resistance characteristics of unconventional and unsymmetrical catamaran hull forms. This thesis attempts to undertake a comparative analysis of resistance characteristics between newly developed unconventional catamaran hull forms of different configurations derived from existing conventional NPL series of round bilge catamaran hull forms (Molland et el 1991). For this a set of catamaran hull forms with the main hull length of 1.6 m, and with a different range of slenderness ratio (L/1/3), B/T ratio are generated by using standard modelling software. The resistance analysis had been carried out by using slender body theory and by using STAR CCM+, a CFD package for Froude numbers 0.25, 0.3, 0.6, 0.8 and 1 respectively and with different separation ratios (s/L) of 0.3 and 0.4. The main objective was to perform a comparative analysis for a wide parameter space which would be encompassing different unconventional hull configurations against conventional hull forms. Literature survey establishes that there is scant literature in public domain to perform resistance analysis on unconventional catamaran hull forms. As this is not feasible due to lack of data in areas that were considered crucial, separate resistance analysis will be carried out for each hull configuration. The new resistance analysis is proposed for a broad range of geometrical parameters especially for asymmetrical hulls so that a designer will be able to make a decision regarding powering prediction in the design stage. Finally, the compared resistance results will attempt to conclude whether unconventional and unsymmetrical catamaran hull forms are more efficient than the conventional hull forms. The results obtained from this analysis shows that asymmetrical catamaran hull forms irrespective of the separation ratio outperformed the normal catamaran hull forms at higher Froude number. But there still lies a conspiracy about the resistance characteristics among the Froude number ranging between 0.4-0.6 which is typically a transition range for high-speed. A finer analysis on the range of Froude number should be carried out in obtaining a closer look over the fluctuation of the resistance at high-speed transition range. It is expected that this study would help to provide a foundation in obtaining greater insight regarding resistance characteristics of unconventional catamaran hull forms especially with regard to slenderness ratio (L/1/3), separation ratio (s/L) and interference effects between the demi-hulls. The conclusions would be beneficial to any early stage designer whose interest lies in advancing the catamaran studies.

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