| Submarine-launched weapons are capable of launch platform hidden,high maneuver ability,combat sudden,heavy firepower and a series of advantages.At present,the main weapon-launching device of domestic conventional tactical submarine which is the main platform for underwater-launched weapon is torpedo tube,and the tube diameter is 534 mm.The tube can launch a torpedo which diameter is 534 and length is around 7000 mm by using hydraulic-balance-launching system.The piston pulling launching device as the launching system for land-based missiles can launch weapons with different sizes.Therefore,how to use the existing torpedo launching system to realize the launch of weapons with different types and different scales has become an important aspect in the field of underwater weapon launching.For anti-ship or cruise missiles with a diameter of 350 mm to 500 mm,in order to adapt the torpedo tube,using missile-carrier or protective canister are two main ways to achieve its underwater-launching.The working principle and process is same with torpedo launching.For smaller missiles with diameter between 150 mm to 250 mm,for example,the missiles for attacking antisubmarine helicopter,not only has the small scale,but it is best to be used in the way of multiple salvo,the use of missile-carrier or protective canister is clearly no longer applicable,thus achieving its underwater launch will become a new topic.There are two significant changes for porting the land-based piston pulling launcher to submarine in order to realize the launching of small air defense missiles.First,the fluid medium changed from air to water.Second,the driving force for the underwater weapon has turned to lifting-beam thrust from the original distributed water pressure acted on torpedo tail.It’s a new type for underwater missile launching which is different from torpedo launching,but also different from the land-based piston pulling missile launching.In order to solve the dynamics related to underwater piston pulling launched missile,a thorough and systematic study were carried out.Completion of the main work and innovation points are as follows:(1)The dynamics and kinematic models of the fluid,the piston and the missile from the piston pulling launcher were established based on the given program of underwater launching system;An appropriate CFD solver was chosen for underwater launch modeling and further investigation.On the basis of rigid body dynamics theory,a re-design work was carried out,together with the dynamic mesh technology,to construct a transient simulation model,which can solve the flow field and missile motion simultaneously in the process of piston pulling underwater launching.(2)Further research on estimations of the applicability of calculating methods,the influence of compute grid and modeling were made.Moreover,a CFD Verification and Validation procedure for underwater launch was presented.The unsteady model used in this paper had been evaluated with this procedure in mentioned aspects above.By comparing with emission test data,the validity of the established numerical model is verified.(3)Detailed studies of the unsteady flow field formation and development both in torpedo tube and the piston pulling cylinder were conducted with the CFD-based unsteady underwater launch model in the process of piston pulling underwater launching.The characteristics of flow field structure are revealed and the formation mechanisms of water hammer and cavitation are obtained.The influence law of water hammer and local bubble process of expansion,contraction,shedding and collapse on the flow structure,ballistic and load characteristics are obtained.(4)Through a series of simulation and analysis,the effect of thrust speciality of the piston pulling cylinder,missile shape and layout form of missile in the tube on launching process are achieved.For example,with the increase of piston pulling cylinder gas flow rate,the degree of the water vapor in the missile tail area is raising,the impact of water hammer pressure on the missile is reducing;By changing the shape of the missile head,the oscillation characteristics of the missile force and torque can be removed by the head vortex,at the meanwhile,the drag force of missile in the process of ejected out of tube can be reduced by changing tail shape;When four missiles are launched in the tube,the degree of the water vapor in the missile tail area is increasing obviously,and it is more difficult to eject the missile out of the tube.Results show that underwater piston pulling missile launching is achievable by matching parameters of launching device and the missile.The whole outcome above have laid a theoretical foundation and provided technical support for the engineering-design of underwater piston pulling launching system. |
