Dynamic Response Of Offshore Wind Turbine With Ship Collision And Performance Analysis Of Protective Device

In recent years,the marine wind power has flourished in the world,and it has become one of the most promising forms of offshore wind energy.It has been highly valued by the national government.The National Energy Bureau’s "13th Five-Year renewable energy" plan for the development of offshore wind power has also put forward specific plans.With the development of global trade,the probability of ships impact the offshore wind turbines near the fairway increases.The offshore wind turbine has a typical heavy top with a tall slender flexible structure.If the support structure is collided to large deformation,which easily cause the dynamic response of the top blade,hub and engine,all of this eventually leads to the collapse of the whole structure,it must be catastrophic.Therefore,the wind turbine after the collision is studied.The dynamic response and the exploration of effective protective device to reduce the harm of ship collision can provide a guarantee for the safe operation of the wind turbine,which holds greater realistic significance and engineering application value.In this paper,the nonlinear finite element method is used to simulate the collision process between the ship and the offshore wind turbine based on ANSYS/LS-DYNA.We analyses the impact performance of the tower structure under different collision conditions and the response of the wind turbine on the top of the tower.The following work is carried out mainly:1.The collision process between Utility Vessel 6514 ship and monopile foundation,tripod foundation and jacket foundation offshore wind turbine is studied.The results show that the displacement and acceleration response of the monopile foundation offshore wind turbine is more obvious than the tripod foundation and the jacket foundation.In the process of collision,the collision area deforms,and the connection part of the pile and the intersection of the inclined pole strain obviously,we should bstrengthened during the design process.From the analysis of the impact depth and contact force of the supporting foundation of the offshore wind turbine,the crashworthiness of the jacket foundation is the best.2.For the monopile foundation offshore wind turbine,the impact velocity,we studied that the change of impact position and the angle of the ship,and analysed that the contact force,the energy change,the impact time,the impact depth and the top response of the tower.The results show that when the impact velocity is at 1m/s,the tower structure has no obvious depressions,and when the impact velocity is 2m/s and above,the tower frame has obvious deformation.When the impact velocity is 4m/s,the deformation of the tower is greater than that of 3m/s,but on the whole,the stress concentration area is smaller.It is said that the corresponding force is carried out through the tower deformation at the moment.With the increase of the collision angle,the deformation energy of the tower structure can be reduced.When the collision angle is 75°,the maximum value of the structural deformation can decrease obviously.The collision angle is small(0°,15°,30°,45°).The impact depth of the tower structure is close after the collision,but the collision angle increases to 60° and 75°.The impact depth of the tower decreased significantly,and the impact depth was more consistent with the deformation energy.The deformation energy of the A collision position support structure accounts for the total energy ratio and the impact depth higher than the B and C collision positions.With the increase of the ship speed,the impact position on the deformation energy of the support structure is becoming smaller and smaller.3.The effect of two constraints on pile foundation with SSI and rigid fixed is compared and analyzed.Through the open source software FAST,the thrust of the wind turbine is calculated and the wave force is introduced into the structure operation.The wave force is calculated by the hydrodynamic software,and the coupling of the structure load is realized by the APDL command,and the wave force is applied accurately.Add to the unit node of the base.The results show that the spring stiffness of the soft clay is small,so the cement placement area and depth of the pile foundation should be increased during the design and construction of the offshore wind turbine,so that the pile and soil should be reduced to suppress the response of the top of the tower.When the wind speed is 11.4m/s,the maximum contact force will be smaller,and the duration of the collision will follow the wind angle.Under the rated wind speed,the change of wind direction angle has great influence on the impact duration.Under the action of waves,the structural deformation of the tower can be increased,but the contact force of the tower top wind turbine response and the impact will be smaller,because the contact force is the interaction of the structural fulcrum and collision force to meet the Newton’s third law.The force and reaction force,the wave action area is more coincided with the collision area of the ship,though the deformation of the structure is larger under the action of the wave,the form and composition of the internal force in the damaged area have changed,so the contact force under the action of the wave is smaller.4.In view of the problem that the marine wind turbine is very dangerous to the collision of the ship,it is put forward to combine the foam aluminum and rubber into the collision avoidance device.The damage of the wind turbine tower and the response of the tower top wind turbine are reduced by the super elasticity of rubber material and the high energy absorption characteristic of the foam aluminum.The following conclusion is drawn: the rubber protective device is used to the wind turbine on the top of the tower.The maximum displacement,speed and acceleration of the tower top,speed and acceleration are reduced by 33%,50% and 23.6% respectively,and the structure deformation of the lower end of the tower can be reduced greatly.The impact depth of the tower is less than that of the 1/10 without protection device.The protective device can avoid the impact force concentrated on the tower,so that the maximum stress is less than the material.In the course of the collision,the structure deformation energy,the maximum contact force,the displacement and acceleration of the top wind turbine at the top of the tower proved that the combination of foam aluminum and rubber combined protection device has the best effect.