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Ship motions and wave-induced loads on high speed Catamarans


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Matsubara, S 2011 , 'Ship motions and wave-induced loads on high speed Catamarans', PhD thesis, The University of Tasmania.

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Advancement in the design of large high-speed ferries demands comprehensive knowledge of
ship motions and wave-induced loads to optimise their structural integrity. This investigation
focused on the fluid structure-interaction problem experimentally to obtain such information.
Motions and loads were investigated by using two different high-speed catamaran models and
a full scale ship. Firstly, a hydroelastic segmented model (HSM) of the INCAT 112 m class
wavepiercer catamaran with centrebow was designed. It was tested in a towing tank for a range
of head seas conditions to determine the motion responses, vertical bending moment (VBM) and
slam loads. A second catamaran model was designed and tested in oblique seas in a model test
basin (MTB) to examine the motions and asymmetric wave-induced loads. Thirdly, full scale
measurements were performed during the delivery voyage of the INCAT 112 m Hull 064 from
Hobart in Australia to Hakodate in Japan, to measure the motions and structural load responses.
The structural dynamic behaviour of the full scale vessel was replicated by the HSM model and
the slamming and subsequent whipping behaviour were successfully modelled. As wave energy
was consumed in the structural vibration of the model, the heave and pitch transfer function
peaks reduced significantly when compared to the rigid configuration. The HSM test results
also showed a strong non-linear motion response, with respect to wave height for this type of
vessel, mainly due to the influence of the centrebow. The peak values for the VBM and slam
loads were confirmed to be proportional to the square of the wave height for large waves. The
MTB test model, which was not fitted with a centrebow, provided linear pitch, heave and roll
motions for varying wave heights. The pitch connecting moment was found to be the dominant
of the asymmetric wave loads and was linear with respect to wave height. During the full scale
measurement programme, slamming phenomena were clearly recorded whilst crossing the Bass
Strait. A reconstruction of the event, from the measured data, indicated that a slam event with
subsequent whipping occurred with a bow down trim. Spectral analysis was used to detect the
response frequencies of the VBM and machinery, with the frequency of the longitudinal mode
increasing as the displacement reduced.
These experimental programmes, encompassing model and full scale measurements, have revealed
valuable insights into the motion and structural dynamic behaviour of large high-speed
catamarans. A comprehensive set of motion transfer functions, VBM and slam loads coefficients
have been obtained, thus providing designers with important slam and wave load knowledge to
aid the improved structural optimisation of these vessels.

Item Type: Thesis - PhD
Authors/Creators:Matsubara, S
Keywords: ship hydrodynamics, ship motion, wave induced loads, slamming vertical bending movement, hydro elastic segmented model
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