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Derwent Park, Australia

Jacobi G.,University of Tasmania | Thomas G.,University of Tasmania | Davis M.R.,University of Tasmania | Davidson G.,Revolution Design Pty Ltd.
Journal of Marine Science and Technology (Japan) | Year: 2014

The slamming behaviour of a large high-speed catamaran has been investigated through the analysis of full-scale trials data. The US Navy conducted the trials in the North Sea and North Atlantic region on a 98 m wave piercer catamaran, HSV-2 Swift, designed by Revolution Design Pty Ltd and built by Incat Tasmania. For varying wave headings, vessel speeds and sea states the data records were interrogated to identify slam events. An automatic slam identification algorithm was developed, considering the measured rate of change of stress in the ship's structure coupled with the vessel's pitch motion. This has allowed the slam occurrence rates to be found for a range of conditions and the influence of vessel speed, wave environment and heading to be determined. The slam events have been further characterised by assessing the relative vertical velocity at impact between the vessel and the wave. Since the ship was equipped with a ride control system, its influence on the slam occurrence rates has also been assessed. © 2013 JASNAOE. Source

Haase M.,University of Tasmania | Binns J.,University of Tasmania | Thomas G.,University of Tasmania | Bose N.,University of Tasmania | And 2 more authors.
Transactions of the Royal Institution of Naval Architects Part A: International Journal of Maritime Engineering | Year: 2012

A new class of fuel-efficient and environmentally friendly twin-hull vessels is currently under development. Compared to high-speed catamarans, a significant reduction in speed combined with an increase in deadweight tonnes will lead to a highly efficient medium-speed catamaran design. Recently-built conventional and high-speed ferries are compared to each other in terms of length, speed, deadweight and transport efficiency to classify the new design. The goal of this study is to find a preliminary macro design point for minimum total resistance by considering the main particulars of the catamaran vessel: block coefficient, prismatic coefficient and slenderness and separation ratios of the demihulls. Publications containing recommendations towards the optimum hull form parameters for moderate Froude numbers are reviewed and existing experimental data analysed to identify parameters for this new class of vessel. Designs with varied L/BOA-ratios and constant deck area are compared to find configurations of low total resistance for carrying a nominated deadweight at a particular speed, the associated change of the light ship weight has been taken into account. Two different model test series of catamaran models have been considered and their resistance curves agreed to each other. Recommendations are made; with the most important being the vessel should not exceed a speed of Fr = 0.35, with optimal prismatic coefficients around C P ≈ 0.5 and low transom immersion. This study presents the preliminary design of medium-speed single and twin-hull vessels for operations close to hump speed. © 2012: The Royal Institution of Naval Architects. Source

Matsubara S.,University of Tasmania | Thomas G.,University of Tasmania | Davis M.R.,University of Tasmania | Holloway D.S.,University of Tasmania | Roberts T.,Revolution Design Pty Ltd.
11th International Conference on Fast Sea Transportation, FAST 2011 - Proceedings | Year: 2011

Knowledge of the magnitude of expected sea loads, particularly slam loads, is a critical component of optimising the structure of large high-speed vessels. Of vital importance is an understanding of the vessel motions since they will directly influence the loads and also the comfort of the passengers and crew. A segmented model of a wave-piercing catamaran has been designed and constructed to obtain experimental values of global motions and loads. Results are presented for the motions, global wave loads and slam loads, with a particular focus on the influence of the centrebow configuration. The motions were found to be distinctly non-linear with respect to wave height; this was due to the immersion of the centrebow in larger waves tending to reduce the heave and pitch motions. The wave loads were found to be dominated by the slam load on the centrebow, varying in magnitude and location with respect to wave conditions. © 2011 American Society of Naval Engineers. Source

Shahraki J.R.,University of Tasmania | Thomas G.,University of Tasmania | Penesis I.,University of Tasmania | Amin W.,University of Tasmania | And 2 more authors.
FAST 2013 - 12th International Conference on Fast Sea Transportation | Year: 2013

Wave-piercing catamarans are used extensively for both defence and commercial sea transportation. Advantages such as large deck area, stability and high speed make these catamarans suitable for transporting roll-on roll-off cargo and passengers. However, issues such as the impact of the bow into the water when operating in large waves, better known as wetdeck slamming, can affect their mission capability and can cause structural damage. Different strategies are used by the designers to reduce wetdeck slamming in catamarans. Wave-piercing catamarans often have a centrebow that provides reserve buoyancy under the wetdeck in the bow to reduce heave and pitch motions and avoid deck diving in following seas. Designing an efficient centrebow is crucial for these vessels to reduce motions and minimise structural loads. To evaluate the effect of various hull forms on motions and slamming loads, a hydroelastic segmented model was designed and constructed. This segmented model is a scaled model of a 112m INCAT wave-piercing catamaran and has two transverse cuts and a separate centrebow. The centrebow segment was equipped with two six degree of freedom force/torque sensors to allow for slam loads to be measured. Three centrebow volumes (lengths) were designed and tested in head seas in the AMC towing tank in regular waves. The results show a significant variation in slam loads when comparing the three centrebow lengths, with the highest loads found on the longest centrebow, caused by larger water volume constrained between the centrebow and demihulls. Results also showed that the longer centrebows have higher pitch motions in slamming conditions. Source

Haase M.,University of Tasmania | Iliopulos F.,University of Tasmania | Davidson G.,Revolution Design Pty Ltd. | Friezer S.,Stuart Friezer Marine Pty Ltd. | And 5 more authors.
Proceedings of the 18th Australasian Fluid Mechanics Conference, AFMC 2012 | Year: 2012

Medium-speed catamarans are the latest development in fast marine transportation. Reliable methods to estimate the calm water performance and to predict the powering for the full scale vessel are necessary. For this paper RANSE-based methods were used to predict the total resistance for medium-speed catamarans for various hull forms, speeds and scales using both an open-source and commercial solver. For the Froude numbers of interest (0:3 < Fr < 0:5) an absolute relative error of 10% and below could be achieved compared to model and full scale test results. Source

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