Numerical Research The Effects On Viscous Flow And Resistance Of Bulb

Mega-yacht is a high value-added product and demand for this kind of ship have continued rising in international market recent years. For the high performances and standards of mega-yacht, researches and developments in this area are needed not only to grab a good economic opportunity in the world's yacht market, but also to meet the demand for enhancing the design and manufacture standard of our shipbuilding industry, bringing development to relevant industries, promoting national economy. As a key technology foundation for autonomous development, research on hydrodynamic performance is no doubt has a significant meaning.Yacht belongs to high-speed vessels in displacement type which have a relative high velocity (Froude number). So reducing the wave resistance is one of the main targets in optimizing the ship hull forms.The target ship of this paper is a 225 feet long luxury yacht. With the help of CFD methods the effects of the bulb and bow lines on viscous flow field and speediness of the yacht are discussed tentaively. Various viscous flow parameters such as the hull streamlines, surface pressure distribution and wake field could be obtained by numerical simulations on the performance of Yachts with different bulb. Variation in viscous resistance and wave resistance is calculated and then analyzed.Numerical calculation includes two parts:the viscous flow calculation without considering the effect of free surface and wave resistance calculation in potential flow model of ideal fluid. In the viscous-flow calculation GAMBIT is used to do preprocess, establish lines, hull surface and computing grids. Under prescribed boundary condition a commercial CFD software FLUENT solver is employed to solve the RANS equations. In order to select a suitable turbulence model and determine the turbulence parameters a large number of calculations are carried out. SHIPFLOW, a kind of specialized software for ship hydrodynamics, is used to calculate wave resistance in potential flow model of ideal fluid.Numerical simulation results show that a properly selected bulbous bow can improve the yacht streamlines, reduce the total resistance and enhance speediness. Noticing that the high-speed yacht has a lower aspect ratio of length to width compared with the ordinary high-speed passenger ships at the same Froude number, attention should be paid on the viscous-pressure resistance besides wave-making resistance when the performance of high-speed yacht with bulbous bow is investigated.