Analysis Of Coupled Dynamic Response Characteristics Of Large Tonnage Shipwreck Salvage Multibody System In Complex Environment

With the rapid development of the economy and shipping industry,marine damage accidents are developing towards large-scale development,and the deep water trend is obvious.Shipwreck accidents need to be salvaged if they meet the following characteristics: the location of the shipwreck near the port or channel causes obstruction to the passage of busy passing ships and there is significant environmental pollution Hidden dangers are of great civil significance.China’s shallow water(within 50 meters)salvage wrecks as a whole,such as "Shiyue" signifies that China has the world’s leading level of shallow water wreck salvage,but there are not many cases of deep water salvage(more than 50 meters water depth)in China.The double barge lifting method is one of the main methods used for salvaging large tonnage shipwrecks.The system composed of two salvage ships and difficult ships has the characteristics of large scale and small spacing.A complex hydrodynamic coupling effect is formed in the wave environment.In this paper,the effect of artificial damping viscosity correction is added based on the potential flow theory,and AQWA software is used to different shipwreck depths.The numerical prediction of the multi-body system motion response and load characteristics is carried out.The specific work and research results of the paper are as follows:(1)Analyze the damage of the sunken ship,and combine the airbag arrangement to estimate the position of the center of gravity of the weight of the sunken ship after it sinks and after the water is released.(2)Introduce the three-dimensional potential flow theory and the potential flow software,select two 12000 t salvage vessels according to the salvage weight,use the modeling software to complete the establishment of the three-dimensional model of the salvage vessel and the sunken ship,verify the mesh convergence,and add viscous damping to Simulate the viscosity of the water body,analyze the impact of four different barge spacings(20.6m,25.6m,30.6m,35.6m)on the movement of the salvage ship and find that the smaller the spacing,the stronger the shielding effect.The consideration of the comprehensive shipwreck width finally selects the 25.6m spacing layout.For this distance,the wreck lifting process was simulated as the wreck is located at different depths(300m,150 m,50m,6m).The movement of the three ships in different frequency domains under regular waves was analyzed.It was found that the movement amplitude increased when the wreck approached the free liquid surface,which was affected by the coupling effect.The impact needs special attention.(3)According to the matching principle of lifting force and salvage weight,the principle of uniform configuration,and the principle of convenient construction,32 lifting cable devices need to be installed,a single set of lifting rated load of 450 tons,a total lifting capacity of 14,400 tons,higher than the weight of 12,000 tons of shipwreck,Based on the commonly used vertical suspension cable design,considering the under-constraint of deep-water sunken ship,the cable stayed cable was designed and compared with it.The research found that the stress distribution of each cable in the cable stayed design was different from that of the vertical cable.At the same time,the cable stayed cable design It can effectively reduce the movement of sunken ship in sway、 heave、 pitch、 yaw of freedom.(4)Based on the analysis of cable-stayed hoisting cables in 150 °,165 ° and 180 ° cocurrent environments,the motion response and the stress of the hoisting cable when the sunken ship is at different depths,the analysis shows that the restraint of the hoisting cable increases as the shipwreck hoists The tension of the hoisting cable increases and the movement of the sunken ship decreases.Due to the dynamic positioning of the actual salvage ship,this article will temporarily lock the salvage ship’s free movement,so the movement of the sunken ship is conservative.Research shows that the hoisting cable can meet the safety factor when the sunken ship is in the deep sea.In shallow water,there are some cases where the load of the hoisting cable is too large.Although it does not meet the safety factor,it can still be hoisted.