Numerical Calculation Of Waves Generated By Multi-hull Ship And The Optimization Of Its Hull Form

In recent years, with the rapid development of the international economy, the freight volume rose dramatically, ships tend to high-speed and multihull. However, the wave of ship on the condition of high-speed will lead to shipping facilities and waterway revetment serious erosion damage, and the large wave resistance also influences ship performance. Through the study of ship generated wave, to explore the methods to reduce the waves and wave-making resistance of ship and design ship type correctly, minimizing the waves and wave-making resistance of ships to achieve the optimization of hull form. The optimized hull form will reduce the erosion damage of shipping facilities and waterway revetment, and the reduction of wave-making resistance will also benefit the ships high speed navigation and improve shipping efficiency.A boundary element method based on the Kelvin source Green function had been employed to calculate the wave of mono-hull, catamaran and trimaran with Wigley hull numerically. The ship generated wave was compared with the experimental data to validate the accuracy and feasibility of the present model. Through varying the ship speed, hull form, demi-hulls spacing of catamaran and side-hull position of trimaran, to calculate and analyze the relation curve of wave height and wave-making resistance coefficient versus Froude number Fn and ship form of mono-hull, the relation curve of wave height and wave-making resistance coefficient versus Froude number Fn and demi-hull spacing D of catamaran, and the relation curve of wave height and wave-making resistance coefficient versus Froude number Fn and side-hull position of trimaran.The ship form parameters of mono-hull have great influences on wave-making resistance. Under the same condition of Froude number Fn, the wave-making resistance coefficient is approximately in linear relationship with the relative ship draft T/L and the relative ship beam B/L, and approximately inversely proportional to the relative ship length L/B and tends to be stable when L/B is large enough. However, the wave-making resistance and wave height will rapidly increase with the increasing of the Froude number Fn, which will not only holdback the high speed sailing but also increases the erosion damage of shipping facilities and waterway revetment.The influence of demi-hulls spacing on the wave-making resistance coefficient of a catamaran is also serious. Due to the ship wave of two demi-hulls can be interference to strengthen or weakened, a reasonable demi-hulls spacing of catamaran will reduce the wave-making resistance. The wave-making resistance and wave height will rapidly increase with the increasing of the Froude number Fn, which will also hold back the high speed sailing of catamaran and increases the erosion damage of shipping facilities and waterway revetment.The side-hull position of trimaran has great influences on wave-making resistance and wave height. With the reasonable optimization of the side-hull position of trimaran, the wave-making resistance will keep small even the Froude number Fn is very large, which in favor of the high speed sailing of trimaran. For the different side-hull position of trimaran, the relation curves of wave-making resistance coefficient and wave height versus Froude number Fn have great differences. In the ship designing, we therefore need to know the basic navigational speed, and then to explore the optimized side-hull position under the condition of the basic navigational speed to make the wave-making resistance minimum.The numerical model in the article is efficient to ship generated wave and wave-making resistance evaluation of ships, and provide an important reference to the design and optimization of hull form of mono-hull, demi-hulls spacing of catamaran, and side-hull position of trimaran.