Wake of a catamaran navigating in restricted waters Geordie Thomas Patrick McSullea Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal 1 INTRODUCTION Maritime transportation has become an essential part of modern society, however there are many negative environmental impacts which people are now seeking solutions for. The main motivations behind investigating this topic include: the safety of people and property in coastal environments, the effect of wake wash on the coastal environment, the social and economic effects due to changes or closure of ferry routes and, lastly, the development of an innovative design tool for naval architects and researchers to study the effects of different ship designs on wake wash. The main objectives of this study were to predict the wakes generated by a set of catamaran designs and their propagation over a given bathymetry using an adapted Funwave code, as well as analysing the main and interacting effects of the Beam, Demi-Beam, Bow Keel Rake and Bow Entry Angle on the wave height and wave energy of the wake wash. These were identified by completing a Design of Experiments analysis in conjunction with the CFD studies. Technical data and support for this research were provided by Incat Crowther, Sydney, as well as various faculties within Instituto Superior Tecnico. The preliminary stage of the research included a CFD study of a single 29.6m hull in a deep-water channel as a monohull and as a catamaran. With this data the pressure distribution used in the Funwave code could then be calibrated by running multiple simulations for different ‘applied’ drafts until agreement was found between the Funwave and CFD results. The main stage of research included 8 CFD simulations of catamarans in a deep-water channel. The hulls were varied according to a half factorial study of four factors mentioned above, each with two levels. These hull models were provided by Incat Crowther, a naval architecture firm based in Sydney, Australia. Using the results of the 8 CFD simulations, the different hulls could be modelled in the Funwave code accurately. Once the ‘applied’ drafts were calibrated for a deep-water channel, the same Funwave code could be re-run for a more complex bathymetry. In the final stage of the research the results of the CFD study were analysed using the DOE methodology and the main and interacting effects were determined. 2 BACKGROUND THEORY 2.1 Wake Wash Studies Today wake wash is well understood, and the form can be predicted with accuracy. In general, the wave pattern generated is more affected by the vessel’s speed/depth ration than the vessel’s form. The Length Froude Number and Depth Froude Number are both useful dimensionless equations which can be used to predict the wave wash form. Length Froude Number,   =  √ (1) Depth Froude Number,  ℎ =  √ℎ (2) When the vessel speed corresponds to a depth Froude number less than approximately 0.75, the speed is said to be sub-critical. As the Froude depth ABSTRACT: High speed catamaran ferries are used throughout the world in confined waters, such as rivers and ports. Wake from these and other small vessels have a variety of effects on the waterways, including deterioration of banks, damage to structures and other vessels, and danger to people close to the shore. An existing code has been used to predict the wake produced by different catamaran hulls in a channel. A CFD study determined the wave heights so that the pressure distribution used in the existing code could be calibrated to accurately predict the wave heights for each hull. Design of experiments methods were utilised to identify the main and interacting effects of the hull characteristics varied between the hulls. Comparison between the existing code and CFD results showed that slight differences between hull characteristics gave different wave heights and these differences could be accounted for by calibrating the pressure distribution. Design of experiments analysis highlighted that of the four factors (beam, demi hull beam, bow keel rake and bow entry angle) demi hull beam had the largest effect on the wave heights and for the values tested, the combination of beam and demi hull beam, i.e. hull spacing, did not have a higher interacting effect than other combinations. Keywords: Catamaran, Funwave, Boussinesq, Wake, Wash