Preliminary Investigation Of Effect Of The Trimaran Configuration On Resistance

In this paper, the effect of the configuration of side hulls of trimaran on its resistance is investigated. First, the effect of the configuration on wave resistance is studied by use of Michell Integral, and then the effect of configuration on total resistance of trimaran is investigated by application of the commercial viscous CFD code FLUENT, with the use of Realizable k-e model, to predict the variation of total resistance with the location of side hulls for the selected two values of Froude numbers (Fr=0.30749, Fr=0.61498) which are typical medium and high velocities for general trimarans. In the process, NURBS is used to fit the surface of total resistance which has 30 reference positions in all 6 longitudinal positions and 5 transverse positions. With the NURBS, contour of total resistance can be easily plotted. The relationships between the layout of side hulls and resistance (total resistance, wave making resistance and viscous pressure resistance) are discussed and analyzed in detail according to the comparison between the results got from turbulence simulation and that from thin ship theory.The comparison of results shows that the contour plots of wave making resistance and that of the turbulence simulation numerical solution of total resistance are similar. This indicates that both the thin ship theory and turbulence simulation are feasible to analyze qualitatively the effect of the configuration of the hulls on resistance. As we can see from the contour plots of pressure resistance and wave making resistance, the variation trend is consistent when the transverse separation between main and side hulls is less than certain value, their variation trends appear some difference when the offset become bigger which indicates that the variation trend of viscous pressure resistance is not in accordance with the trend of wave making resistance.The results calculated with turbulent numerical simulation reveal the rules of resistance relating to arrangement of side hulls. The analyzed rule in this paper is consistent with that the other literatures previously published. It also shows that the boundary condition, grid and turbulence model used in this paper are applicable and feasible for evaluating the configuration and resistance prediction of trimaran hulls. The author thinks all the work in this paper can provide some reference for the further study of resistance of trimaran.