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Bennetts L.G.,University of Adelaide | Yiew L.J.,University of Adelaide | Meylan M.H.,University of Newcastle | French B.J.,National Center for Maritime Engineering and Hydrodynamics | Thomas G.A.,National Center for Maritime Engineering and Hydrodynamics
Proceedings of the 19th Australasian Fluid Mechanics Conference, AFMC 2014 | Year: 2014

An experimental model of wave-induced collisions between two sea-ice floes is presented. The model was implemented in a laboratory wave basin. Monochromatic incident waves were used, with frequencies between 0.5 Hz and 1.5 Hz, and wave heights 20 mm and 40 mm. An algorithm is proposed to identify collisions and collision velocities from recorded floe motions. Collisions are shown to be strongest and most frequent for mid-range frequencies and the larger wave height.

Thomas G.,National Center for Maritime Engineering and Hydrodynamics | Kibby L.,National Center for Maritime Engineering and Hydrodynamics | Ford A.,National Center for Maritime Engineering and Hydrodynamics | Binns J.R.,National Center for Maritime Engineering and Hydrodynamics | And 2 more authors.
Ships and Offshore Structures | Year: 2011

A new concept uses a large catamaran, Gas Cat, as a floating natural gas processing, storage and offloading facility. The concept design of the vessel is based on two retrofitted very large crude carriers allowing for the processing and storage of 1 million bbls of condensate and approximately 240,000 m 3 of liquid natural gas. Key to the development of this concept is the accurate estimation of the wave-induced cross-demi-hull loads experienced by the catamaran in a variety of operational scenarios. Model experiments were conducted in the model test basin of the Australian Maritime College using a 1:78 scale model of two full-form hulls, converted into a catamaran configuration, to measure the wave-induced forces and moments. Tests were conducted in head, beam and oblique seas for two hull spacings and a range of wave heights. The experimental results show that for the range of wave conditions tested, good linearity of the forces and moments can be expected with respect to wave height. This allows the results to be used to determine expected loads for a range of wave conditions. Changes in demi-hull separation were found to have little influence on the measured cross-demi-hull loads. Forces and moments were the least for the head sea condition; therefore, in order to minimise the wave-induced loads on the vessel, it is recommended that it be allowed to weathervane with the prevailing swell direction. The forces and moments which may be expected in Timor Sea 10,000-year return storm conditions have been estimated based on the model results. These provide valuable data for the preliminary design of an appropriate structural configuration for the vessel. © 2011 Taylor and Francis Group, LLC.

Meylan M.H.,University of Newcastle | Yiew L.J.,University of Adelaide | Bennetts L.G.,University of Adelaide | French B.J.,National Center for Maritime Engineering and Hydrodynamics | Thomas G.A.,University of Adelaide
Annals of Glaciology | Year: 2015

A theoretical model and an experimental model of surge motions of an ice floe due to regular waves are presented. The theoretical model is a modified version of Morrison's equation, valid for small floating bodies. The experimental model is implemented in a wave basin at a scale 1:100, using a thin plastic disc to model the floe. The processed experimental data display a regime change in surge amplitude when the incident wavelength is approximately twice the floe diameter. It is shown that the theoretical model is accurate in the high-wavelength regime, but highly inaccurate in the lowwavelength regime.

Dawson E.,Defence Science and Technology Organisation, Australia | Morris B.,Defence Science and Technology Organisation, Australia | Duffy J.,National Center for Maritime Engineering and Hydrodynamics
RINA, Royal Institution of Naval Architects - International Maritime Conference 2012, Pacific 2012 | Year: 2012

The manoeuvrability and control of marine vehicles, whether commercial or naval platforms, is critical to their safe, efficient and effective operation. It is a regulatory requirement of the International Maritime Organization that specific craft meet prescribed manoeuvring performance criteria to mitigate the risk of collision and catastrophic failure. In-harbour operational efficiency in the marine transport sector is a significant financial driver, while Naval war-fighting doctrine demand that surface combatants can out-manoeuvre and outperform the myriad of present day and future threats to enable them to maintain their dominance as a naval deterrent. This poses the question: are we as a nation in a position to assess and understand the manoeuvring performance of marine vehicles to the level required by the statutory, commercial and defence stakeholders? If not, then what would it take to bridge that capability gap and is an investment into the development of an indigenous capability the best solution? To date, science and industry have developed methods to analyse and evaluate the manoeuvring and control characteristics of marine vehicles. These range from physical experimentation to systems identification and more recently, advanced numerical simulation. The abilities and limitations of these methods are generally well understood such that they can be appropriately implemented. In this paper, systems thinking is utilised to explore the complex issue of how to develop an indigenous marine vehicle manoeuvring analysis and evaluation capability. The strategic and technical aspects surrounding this capability, along with some of the risks involved, are assessed and discussed. Concept solutions to fulfil the capability's requirements are proposed with the aim to provide the best outcome based on the needs of the maritime industry and its customers.

Allan C.,Griffith University | Symes M.,National Center for Maritime Engineering and Hydrodynamics | Downing J.,University of Tasmania
30th Annual conference on Australian Society for Computers in Learning in Tertiary Education, ASCILITE 2013 | Year: 2013

The Australian Maritime College (AMC) has a major objective to innovate and build better practice in e-learning by developing high quality learning for anyone, anytime, anywhere. One strategy that the AMC has undertaken to achieve this is to fund a number of e-initiatives (learning and teaching projects being undertaken using digital technologies) each year between 2012 and 2016. To gain maximum long-term benefit from this project it is essential to develop an evidence based approach, studying each initiative’s effectiveness and derive learning and teaching (L&T) principles for using technology within the maritime context. This paper describes a project to explore, implement and document e-learning principles relevant to the maritime education context. The project uses an educational design-based approach. At conclusion of the project it is expected that a number of learning designs and guiding principles for maritime education will be developed. © 2013 Christopher Allan, Mark Symes, and Jill Downing.

Hutchison C.,National Center for Maritime Engineering and Hydrodynamics | Binns J.,National Center for Maritime Engineering and Hydrodynamics | Duffy J.,National Center for Maritime Engineering and Hydrodynamics | Brandner P.,National Center for Maritime Engineering and Hydrodynamics
4th High Performance Yacht Design Conference 2012, HPYD 2012 | Year: 2012

With the ever evolving design space, the need for quality data for designers has never been more important. To realize this need, designers typically turn to one of two techniques either: experimental fluid dynamics, typically using either towing tank or wind tunnel testing; or computational fluid dynamics. It is becoming increasingly easy, especially with the ever increasing power of computers and the visually attractive output, to take the decision to undertake computational fluid dynamics analyses. Whilst on the surface this may seem an easy decision to make, certainly easier than to undertake towing tank tests, there are some strong arguments to suggest that simply undertaking a computational fluid dynamics analysis as an a-priori solution is not without problems or dangers. Extrapolation of experimental fluid dynamics drag results to full-scale for marine craft has traditionally involved attributing components of the total force to "viscous" and "inviscid" regimes. These components are then scaled with the Reynolds and Froude numbers respectively using a zero Froude number extrapolation to separate the two. However, this division of forces does not correlate exactly with shear and normal pressures on a body due to fluid flow, which sum to give drag. Nor can each of the "viscous" and "inviscid" components be attributed to strictly Reynolds and Froude number dependent effects, respectively.

Thomas G.,National Center for Maritime Engineering and Hydrodynamics | Duffy J.,National Center for Maritime Engineering and Hydrodynamics | Lilienthal T.,National Center for Maritime Engineering and Hydrodynamics | Watts R.,National Center for Maritime Engineering and Hydrodynamics | Gehling R.,Australian Maritime Safety Authority
Ships and Offshore Structures | Year: 2010

Parametric rolling in head seas can cause serious safety issues for ships with the possibility of cargo shift, damage and difficult working conditions for crew. This work investigates the prediction of its occurrence and the factors that influence its onset and magnitude. It also seeks to establish the effect of bilge keels on containerships. The threshold boundaries for the inception of parametric roll, for a typical containership operating in Australian ports, are established using the Mathieu equation. Good agreement was found between the numerical predictions and results from a set of towing tank experiments. Fitting of bilge keels to the containership model was found to be an effective way of reducing the roll angles induced by parametric roll, and in some cases their presence can prevent its onset. A simplified method for use by masters to avoid the onset of parametric roll is also presented. © 2010 Taylor & Francis.

Wang Y.,National Center for Maritime Engineering and Hydrodynamics | Nguyen H.D.,National Center for Maritime Engineering and Hydrodynamics | Chai S.,National Center for Maritime Engineering and Hydrodynamics | Khan F.,National Center for Maritime Engineering and Hydrodynamics
2015 Australian Control Conference, AUCC 2015 | Year: 2015

This paper presents a rudder-roll stabilization system utilizing Radial Basis Function neural network (RBFNN) for course keeping and roll damping. Roll motion of a vessel sailing under severe weather conditions has adverse effects on crews' health, cargoes and safety, thus it must be damped as much as possible. A new control algorithm for both course keeping and roll damping is proposed based on the RBFNNs. In order to realize the proposed rudder roll stabilization system, a nonlinear mathematical model of a container vessel with effects of wave disturbance is used to simulate the proposed rudder roll stabilization system which consists of two controllers implemented in parallel, one is the autopilot for course keeping and the other is roll damping controller. The performance and robustness of the proposed control system is investigated by taking consideration of the effects of external disturbance. The simulation studies are designed to verify the improved performance of the proposed rudder roll stabilization system and to validate its efficiency of course keeping and roll motion reduction. © 2015 Engineers Australia.

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