| With the rapid development of ship technology,high standards are required for the diversification of ship lines,rapidity,energy efficiency and safety.At present,the complex marine environment has become the inevitable work status of most transport ships in the world.For the consideration of ship rapidity,energy efficiency and safety,the research on the problems of wave load and ship motion encountered by ships in the sea navigation is a great significance,which will also be the focus of this paper.In this paper,81000 Dead Weight Bulk Carrier(81000 DWT BC)is taken as the research object.The flow field around the 81000 DWT BC is simulated by the method of computational fluid dynamics(CFD),and then the resistance,movement and the distribution of flow field at the free surface of the research object in the simulation flow field are analyzed,Because the actual marine environment is relatively complex and changeable,and the ship is not only under the wave load,but also under the wind load.Therefore,according to the actual situation,taking into account the situation of free surface caused by the simultaneous action of wind and wave,the method of VOF two-phase flow is used to trace and capture the free surface,and the location is numerical simulation and analysis of Bulk Carrier under free surface are carried out.Specific process:First of all,in this paper,the resistance,motion and flow field distribution of Bulk Carrier under static water are simulated and analyzed under different speed,load condition and turning angle,and the resistance increases with the increase of speed and draught.At the same time,it is verified that the friction resistance of low Froude number ship always occupies the dominant position in the limited speed.When the angle is 90°,the resistance reaches the maximum critical value,and the total resistance is almost provided by the pressure resistance of the incident fluid.At this time,the ship is in a dangerous state.Secondly,the Bulk Carrier is transformed from a static water area to a wave area,and the simulated wave velocity method is adopted at the entrance to make waves and eliminate the boundary.In this paper,the wave forces and static water resistances of the ship are compared and analyzed,so that the resistance increase of the ship under three wave conditions is obtained.Then,the dimensionless resistance increase coefficient,heave and pitch are divided.The results show that the heave and pitch of the ship vary with the speed and draught when the wavelength to length ratio λ/L=1.1 is near the middle wavelength.At the same time,the wave resistance of the Bulk Carrier reaches the peak value under this wavelength condition,so it can be concluded that the wave resistance increase of the ship is mainly caused by the radiation effect.Finally,the wave resistance increase coefficient with different wavelength conditions is combined.With the change of speed and draught,the maximum resistance increase of Bulk Carrier under different speed and load conditions is obtained.The results show that it is of practical significance to change the speed,draft and wavelength of the ship to increase the resistance under the wave load,but the most intuitive factor affecting the increase of the resistance is the ratio of λ/L under the medium wavelength.At the same time,reasonable control of the speed and draft can also reduce the impact of the increase of the resistance on the ship,so as to achieve the effect of energy conservation and emission reduction. |
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