الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Catamarans and other multihull configurations have a better performance regarding speed, resistance, manoeuvrability and transverse stability compared to mono-hull configurations. In this study, a CFD simulation of the flow about a displacement catamaran model (Delft 372 catamaran model) is conducted over a range of forward speeds by numerical solution of the Reynold Average Navier-Stokes equation (RANSE). Shear Stress Transport (SST) turbulence model is selected, and the volume of fluid (VOF) method is adopted to capture the free surface flow about the catamaran.In this study, the total resistance of the twin-hulls vessel is calculated at low Froude numbers, medium Froude numbers and high Froude numbers of the operating range of the catamarans, using three different meshes with three different numbers of elements are set, namely; a Coarse, a Medium and a Fine mesh. Followed by mesh convergence study in order to calculate the numerical Uncertainty. and then, a Validation of results is achieved by comparison with experimental data available in the literature.The aim of the study is to investigate the effect of separation-length ratio and non-parallel configuration of the demi-hulls on the total resistance and wave pattern generated by the catamaran over a range of forward speeds. Subsequently, the Response Surface Method for optimization is applied to the obtained results at a particular Froude number and over a selected range of separation-length ratio and non-parallel configuration of the demi-hulls to provide minimum total resistance.Overall, a satisfactory mesh size convergence is achieved with low obtained Uncertainties and good agreement between the numerical and experimental results is achieved where, excellent agreement is observed at medium and high Froude numbers. The influence of separation-length ratio on the total resistance is contrary which the twin hull’s total resistance decreases as the separation-length ratio increases, and same effect of the separation-length ratio on total resistance is observed on the heights of generated waves by the catamaran. The effect of the nonparallel angle α° on the total resistance is positive over a small range varying from 0° to -2.5° according to the separation-length ratio. In other words, the minimum total resistance was obtained when the catamaran demi hulls’ bows are slightly rotated inwards closer to one.Optimization of the obtained results has shown that; there is an optimum value for α° that provides minimum resistance for each separation-length ratio and Froude number. The applied optimization method always nominated the chosen upper limit of the separation-length ratio as an optimum. While the optimization method has determined the optimum non-parallel angle to be equal to α°= -0.988°. Obtained results are satisfactory with a reduction in the optimized total resistance of about 5% as compared to the original configuration of the catamaran.