Research On Resistance And Motion Characteristics In Waves Of New Type Hybrid Trimaran

With the gradual depletion of land resources,human demand for marine energy and marine applications is increasing,and this has led to the rapid development of the shipping industry.People has also put forward higher requirements on the speed,seakeeping and comfort of ships.Due to their excellent comprehensive navigation performance,high-performance ships are developing rapidly and new types of ships are continuously emerging.Multi-hull ships and hybrid multi-hull ships have become the focus of research in recent years.The research and forecast of their hydrodynamic characteristics are also prepared valued.At present,the trimaran has a general consensus on broad application prospects in both military and civilian applications due to its excellent speed,good seakeeping characteristics and large-scale benefit;the small waterline area ship has outstanding seakeeping performance,but its relative obvious shortcoming is that it has greater resistance in still water,and is more sensitive to changes in draft.In this paper,the ship-generating technology and the smoothing method are applied to form the semi-small waterplane transom hybrid trimaran by this two ship types in an attempt to balance the high speed of the trimaran with the excellent seakeeping performance of the small waterline area ship.The novel concept of this hybrid trimaran is of great significance in the initial design stage for its research on the resistance,the distribution of flow field and the response characteristics of motions in waves.In this paper,the forecast and research on the hydrodynamic performance of the new hybrid trimaran are carried out.First,based on the theory of viscous fluid mechanics,the CFD method is adopted to study ship resistance,viscous flow field distribution,numerical wave making method and the prediction of ship motion responses in waves.By using the validated method,the effects of stern shapes on performance of the trimaran is studied according to the flow field and pressure distribution and seakeeping requirements.Then the influence of different stern hybrid schemes on the resistance and navigation state in calm water is discussed,and the influences of speed,wavelength and stern hybrid schemes are discussed based on the amplitude of pitch,heave and acceleration of the center of gravity to show the motion response characteristics in regular head waves.According to the hydrodynamic performance both in calm water and waves,the better hybrid scheme is selected.In order to improve the longitudinal motion performance in waves of this ship type,the T-foil type with better performance is added to it,and then the influence of longitudinal and vertical installation position,the direction and angle of attack of T-foil on hybrid trimaran is further analyzed and studied.The results show that,the further combination of the transom stern has a certain effect on improvement of the ship speed and the navigation state in calm water.The trimaran scheme with wider stern and larger longitudinal oblique angle is better in both resistance and motion response in the calm water and waves.The amplitudes of the motion responses in waves,such as the pitch,heave and acceleration of the center of gravity of hybrid trimaran all show a certain regularity,and are still large at high speed.After installing the T-foil,compared with the installation position,the angle of attack is the main factor that affects the hydrostatic resistance and navigation state of the trimaran.The installation of the T-foil can significantly reduce the values of the motion response of the trimaran at the larger wavelength,the installation position and the angle of attack decrease the values in different degrees.As for the value at smaller wavelength,T-foil has little effect and the effect of ship form is more obvious.The new hybrid trimaran installed T-foil with a reasonable position and angle of attack has a slight increase in resistance,but has advantages in terms of seakeeping performance.