Ship motions and wave-induced loads onudhigh speed Catamarans

摘要

Advancement in the design of large high-speed ferries demands comprehensive knowledge ofudship motions and wave-induced loads to optimise their structural integrity. This investigationudfocused on the fluid structure-interaction problem experimentally to obtain such information.udMotions and loads were investigated by using two different high-speed catamaran models anduda full scale ship. Firstly, a hydroelastic segmented model (HSM) of the INCAT 112 m classudwavepiercer catamaran with centrebow was designed. It was tested in a towing tank for a rangeudof head seas conditions to determine the motion responses, vertical bending moment (VBM) andudslam loads. A second catamaran model was designed and tested in oblique seas in a model testudbasin (MTB) to examine the motions and asymmetric wave-induced loads. Thirdly, full scaleudmeasurements were performed during the delivery voyage of the INCAT 112 m Hull 064 fromudHobart in Australia to Hakodate in Japan, to measure the motions and structural load responses.udThe structural dynamic behaviour of the full scale vessel was replicated by the HSM model andudthe slamming and subsequent whipping behaviour were successfully modelled. As wave energyudwas consumed in the structural vibration of the model, the heave and pitch transfer functionudpeaks reduced significantly when compared to the rigid configuration. The HSM test resultsudalso showed a strong non-linear motion response, with respect to wave height for this type ofudvessel, mainly due to the influence of the centrebow. The peak values for the VBM and slamudloads were confirmed to be proportional to the square of the wave height for large waves. TheudMTB test model, which was not fitted with a centrebow, provided linear pitch, heave and rolludmotions for varying wave heights. The pitch connecting moment was found to be the dominantudof the asymmetric wave loads and was linear with respect to wave height. During the full scaleudmeasurement programme, slamming phenomena were clearly recorded whilst crossing the BassudStrait. A reconstruction of the event, from the measured data, indicated that a slam event withudsubsequent whipping occurred with a bow down trim. Spectral analysis was used to detect theudresponse frequencies of the VBM and machinery, with the frequency of the longitudinal modeudincreasing as the displacement reduced.udThese experimental programmes, encompassing model and full scale measurements, have revealedudvaluable insights into the motion and structural dynamic behaviour of large high-speedudcatamarans. A comprehensive set of motion transfer functions, VBM and slam loads coefficientsudhave been obtained, thus providing designers with important slam and wave load knowledge toudaid the improved structural optimisation of these vessels.