Research And Analysis Of The Ship's Buffer Bulbous Bow Structure

Booming international trade makes the shipping industry have a great progress. However, as the increase of ships in number, speed and tonnage, ship collision accidents are also increasingly frequent, which pose a serious threat for personnel, marine equipment, marine environment. Solving ship collision problems not only can ensure the safety of personnel at the sea, but also prevent pollution of the marine environment and improve the economic benefit of shipping industry.Although ships apply the design of double hull tanker in the accidents of large vessels'high-energy collision, the capability of ships' walls for collision energy absorption still can not meet the requirements for withstanding kinetic energy of hitting vessels, which would cause the inner shell rupture and crude oil leak. Therefore, the designing of the bow buffer structure is significant for improving ships'survivability in collision accidents, preventing the marine pollution caused by hull rupture and reducing the cost of ship construction.The studying methods of buffer bulbous bow include simplified theoretical method, experimental method and numerical simulation of finite element. This paper will adopt the method of numerical simulation of finite element for the bulbous bow collision analysis to gain relevant studying results. Now the main crash simulation software includes LS-DYNA, ANSYS, MSC.DYTRAN, ABAQUS, MSC.MARC etc. This paper uses mainly analysis software LS-DYNA with the explicit finite element method for crash simulation.This paper uses simplified model of bulbous bow and the real ship model to collision simulation analysis for bulbous bow structures which adopt prismatic bow column, intermittent deck design and both combination design, compares and analyzes the contact force changes, destroying deformation and energy absorption of traditional structure, prismatic bow column, intermittent deck design and both combination design.Prismatic bow column structure on the one hand reduces contact force the bow suffered in the initial crushing, which makes the bow easier to deformation at the early time of collision, on the other hand the deformation of the bow extended contact areas of the bow and the crushed ship and reduced the contact stress so that more members of the ship were involved in the collision and deformation, which improved the overall capability for energy absorption; Intermittent deck design reduces the overall longitudinal stiffness of the bulbous bow, which is easier to deformation than the bow of traditional deck as the enhancement of contact force in the process of collision; The combination bow of prismatic bow column and intermittent deck absorbs advantages of both buffer design, on the one hand the prismatic column occurs deformation under the lower contact force and expands contact areas at the early time of collision, which can prevent the crushed ship to rupture at the early time of collision, on the other hand the design of intermittent deck further reduces the peak of the deformation contact force of the bow in the process of collision, increases significantly the capacity of buffer deformation, lowers the kinetic energy of collision absorbed by the crushed ship and improves the surviving ability of the crushed ship in the collision accident.