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Non-linear unsteady wave loads on large high-speed wave piercing catamarans

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Amin, W (2009) Non-linear unsteady wave loads on large high-speed wave piercing catamarans. PhD thesis, University of Tasmania.

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Abstract

The current work investigates the slamming characteristics of wave piercing catamarans
through the analysis of sea trials data of the 98 m Incat sea frame “Hull 061”, built in
Tasmania, Australia and currently serving in the US Navy combat fleet. The importance of
this sea trials data is that the ship was tested in severe sea conditions to assess her suitability
for military operations and to define her operational envelope. New signal processing
techniques such as Wavelet Transforms are used in analysing slamming data for two main
purposes, slamming identification and modal analysis in time and frequency domains
simultaneously. The Wavelet Transforms were found superior to conventional signal
processing tools such as Fast Fourier Transform and Short Time Fourier Transform.
The structural strength of wave piercing catamarans is studied by introducing a novel sea
trials analysis for structural performance assessment in an attempt to simulate real loading
conditions. The methodology was tested on normal linear wave loading (without
slamming) and was found satisfactory. A “Reverse Engineering” approach is introduced to
predict slamming loads during sea trials by using the capabilities of Finite Element Analysis
using the well known software PATRAN/NASTRAN1. To increase the efficiency of this
approach, the load parameters, spatial location and distribution, were investigated through
model tests of a similar but larger 112 m Incat hydro-elastic model in the Australian
Maritime College towing tank facility. Based on pressure measurements, proper slam load
models can be more accurately and efficiently introduced in the finite element analysis.
Quasi-static analysis was first performed to examine its suitability to analyse such fast time
varying loads. Difficulties in comparison procedures between numerical simulations and
trials data have strongly highlighted the need for dynamic analysis. Direct transient dynamic
analysis was performed using the dynamic solver of the same software package. Good
agreement with trials data was found. The suggested procedure and slamming loading
patterns used in the numerical simulation is then verified and can be regarded as a solid
base for verification of other theoretical design models.

Item Type: Thesis (PhD)
Additional Information:

Copyright © the Author. For any requests regarding this thesis, please contact the author on waiamin@utas.edu.au

Date Deposited: 06 Dec 2011 01:21
Last Modified: 11 Mar 2016 05:53
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